Optical metrology in the conflict between desire and reality

摘要

In the context of measurement technology, optical methods have a number of unique features. On the other hand the user is faced with serious challenges. One of the biggest challenges that currently attracts high attention in both the technical as well as life sciences, relates to exceeding the physical limits of resolution. Nowadays people prefer to talk about super-resolution. However, this concept creates an often excessive expectation, since this way only the diffraction limit can be achieved in many practical cases. Not to forget are those negative consequences that arise from the high information density in optical signals. The nature of light and its fascinating interaction with matter that makes our visual sense on the one hand the most valuable information carrier, often prevents on the other hand, the metrologically correct interpretation of the results. Nevertheless, it can be proven by numerous examples that no alternative to the optical principles exists. Because critical structures are getting smaller and functional surfaces are becoming increasingly complex, the wavelength of light provides the most flexible and traceable standard to cope with the challenges. But the potential of optical methods, often seduced to an overload of the wish list or to unrealistic promises. Therefore, this paper is dedicated to the tension between desire and reality in optical measuring techniques.