Enhancing precision in line-scan chromatic confocal sensors through bimodal signal pattern

• Published in: Optics and laser technology Vol. 180; p. 111417
• Main Authors: Dai, Jiacheng, Zhong, Wenbin, Zeng, Wenhan, Jiang, Xiangqian, Chang, Suping, Lu, Wenlong
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2025
• Subjects: Chromatic confocal measurement; Optical sensors; Precision engineering; Optical sensors; Chromatic confocal measurement; Precision engineering
• ISSN: 0030-3992
• DOI: 10.1016/j.optlastec.2024.111417

•The small numerical aperture and neighborhood crosstalk from line-scan chromatic confocal measurement are the primary causes for the unimodal feature degradation on the spectral power distribution.•With the unimodal feature degradation, the focused wavelength as an intermediate variable cannot transmit distance information robustly.•The bimodal signal feature obtained by the filter window offset leads to a more robust intermediate variable.•The experiments show that the bimodal signal pattern can achieve a 40% precision improvement in line-scan chromatic confocal measurement. The peak feature of spectral power distribution signals from conventional chromatic confocal measurement degrades significantly as the scanning mode change, which is detrimental to the accuracy and precision of the line-scan chromatic confocal sensor. A bimodal signal pattern is proposed in this paper to solve the peak feature degradation problem. In the bimodal signal pattern, two peak features with smaller full width at half maximum are obtained by offsetting the filter slit. This results in more robust feature localization and more accurate measurement output from the line-scan sensor. Precision calibration experiments conducted on a self-developed line-scan chromatic confocal sensor reveal a remarkable 40% improvement in precision when employing the bimodal signal pattern compared to the traditional unimodal signal pattern with the same hardware configuration.