With increasing digitalisation of engineering and the development of smart manufacturing, precision metrology is gradually moving away from the laboratory into real-world environments and production platforms. Interferometry and focus detection are the most popular optical techniques for these types of application due to their non-destructive measurement, high resolution, and fast response. In this article, we discuss their basic principles, limitations and challenges, and new opportunities. Motivated by the rapid development of artificial materials, the application of metasurfaces to drive a new era for future miniaturisation of optical systems becomes suddenly viable. The article discusses advances in modern miniaturisation of optical techniques; and introduces an approach for evolving to a future using metasurface optics. Optical principles and feasibility studies are included in the discussion.