Single-Shot Surface Topography Measurement Using Two-Color Fluorescence

Abstract A single-shot surface topography measurement technique based on two-color laser-induced fluorescence is proposed for in situ and on-machine applications. In fluorescence intensity-based measurements, the spatial nonuniformity of the excitation light often degrades the measurement accuracy. To address these issues, the proposed technique uses the intensity ratio of two fluorescence emission bands generated by mixed fluorescent dyes with spectral reabsorption characteristics. The measurement principle is theoretically formulated, and its robustness against variations in the surface material and illumination conditions is analyzed. A scanless single-shot optical measurement system employing a color CMOS camera is developed, enabling full-field surface topography acquisition in a single exposure. Calibration is performed using a reference step height without requiring precise knowledge of optical parameters. The experimental results demonstrate that the proposed two-color fluorescence technique suppresses apparent height errors within approximately ± 0.5 µm. Measurements of flat and structured surfaces confirm improved robustness and applicability to microscale surface topography measurement under practical manufacturing conditions.