Coherence scanning interferometry (CSI) is a powerful, highly accurate non-contacting metrology method, which uses a broadband light source and combines vertical scanning with optical interferometry techniques, to achieve a three-dimensional surface measurement with sub-nanometre precision. Nevertheless, CSI has shown limited detectability when dealing with surfaces featuring high slopes, due to the limited numerical aperture of its objective optics.
Additive manufacturing (AM) is an example of a challenging application for CSI, wherein components produced by AM can have very rough surface texture with local slopes well beyond the NA limit. Diffuse, dissimilar, translucent, or porous surfaces also represent a challenge. These properties can significantly suppress the strength of any interferometric signals. However, most recent advances in CSI further expand the range of measurement parameters, offering significantly improved sensitivity to overcome these limitations.
This project consists of two main objectives:
- Development of guidelines to upgrade topographic measurement of CSI for difficult-to-manufacture applications.
- Improvement of the correlation between CSI and other surface metrology methods.
Carlos Gomez, Rong Su, Adam Thompson, Jack DiSciacca, Simon Lawes, Richard Leach, “Optimization of surface measurement for metal additive manufacturing using coherence scanning interferometry,” Opt. Eng. 56(11), 111714 (2017), doi: 10.1117/1.OE.56.11.111714