Efficient scanning strategy via graph coloring for crosstalk mitigation in chromatic confocal measurement

Chromatic confocal measurement (CCM) has attracted widespread attention due to its advantages, including high axial resolution and contactless measurement. The programmability of digital micromirror devices (DMDs) enables array-based chromatic confocal systems to suppress crosstalk effectively, which is a critical advantage that distinguishes them from large-area array systems. However, the traditional raster scanning strategy suffers from excessive scanning frames and low efficiency when facing the asymmetry of spectral crosstalk caused by factors such as diffraction in optical systems. This paper proposes a DMD scanning strategy based on the DSATUR graph coloring algorithm. The interference relationship between micromirror units is modeled as a graph. By solving the graph coloring problem, the minimum number of scanning frames and the corresponding scanning patterns are determined. Building upon this foundation, we incorporate an analysis of the experimental spectral crosstalk into the interference model, which in turn enables efficient and crosstalk-free scanning path planning. The proposed method is validated on a 1.5×1.5 mm² plane mirror, a 0.9 mm height difference step, and a metal-engraved letter "V" structure. The results demonstrate that the proposed method significantly reduces the number of scans while maintaining reconstruction accuracy, thereby improving the measurement efficiency.