Single-shot high speed aerial chromatic confocal metrology sensor

Abstract

Chromatic confocal metrology is a widely established optical metrology technique, which allows for noncontact, high-speed three-dimensional surface profiling without the need of mechanical depth scanning. However, current methods are limited by the use of some sort of surface scanning method with mechanically moving parts. Furthermore, the setups involve a spectrometer setup, either through prisms, gratings, or multispectral cameras. This drastically limits the simultaneously measureable positions in lateral direction, as the spectrometer setup will utilize one spatial dimension for the wavelength domain. We present a method for chromatic confocal metrology that enables high-speed and high-resolution one-shot aerial surface metrology. This method is scalable with respect to measurement range in axial as well as in lateral direction and in the number of measurement points that can be measured simultaneously. After deriving the theoretical basis of the approach, a virtual optical design with a field of view of 10 mm × 10 mm and a depth range of 1.5 mm with roughly 1000 measurement points, based mainly on off-the-shelf components will be presented. This virtual system design was used to perform various simulations and explain the design process and considerations as well as the expected system response of the proposed system.