Enhancing measurement precision of superluminescent diode-based chromatic confocal sensor by real-time spectral correction

Abstract

Chromatic confocal sensors are widely used in high-resolution, non-contact distance measurements. Despite their advantages, conventional implementations often suffer from low light utilization efficiency and instability in the illumination spectrum, both of which degrade measurement accuracy, particularly when using broadband semiconductor sources such as superluminescent diodes. In this study, we address these limitations by introducing a chromatic confocal system that incorporates a high-brightness SLD alongside a real-time spectral correction mechanism. The proposed optical setup features a dual-beam spectrometer capable of simultaneously capturing the reflected axial intensity signal and the intrinsic spectrum of the light source using a global shutter camera. This architecture enables frame-by-frame normalization of the measured signal, reducing the impact of spectral fluctuations and inherent source nonuniformities. Simulation and experimental results demonstrate that, in the previously introduced system, this method reduces the wavelength-to-distance encoding error from $\pm$0.4 µm to below 0.2 µm, and decreases distance uncertainty due to source instability by 20%. The system is particularly suited for applications involving low-reflectivity surfaces or requiring high-speed scanning at rates up to tens of kHz.