Signal Processing and Artificial Intelligence for Dual-Detection Confocal Probes

The confocal probe is one of the most well-used optical sensors for displacement/position measurement as well as for mapping of three-dimensional microstructured surfaces and internal structures. A dual-detection configuration employing two detectors is often used in the state-of-the-art confocal probes to achieve wider measurement ranges, higher resolutions, better accuracies and faster measurement speeds. In this paper, the motivation and benefits for development and employment of the dual-detection confocal probes, as well as the investigation of the detector positions, are first presented. The signal processing methods associated with the dual-detection confocal probes are then categorized into the difference-type and the ratio-type, followed by descriptions on the features of each method. Finally, signal processing based on artificial intelligence and machine learning for the confocal probes are presented.