Improving Elemental Imaging on Uneven Material Surfaces

Can imaging systems improve the accuracy of elemental imaging on uneven surfaces?

According to a recent study published in the journal Talanta, the answer is yes. In this recent study, a team of researchers from Zhejiang A&F University, Tsinghua University, and Changchun University of Science and Technology have developed an auto-focusing laser-induced breakdown spectroscopy (AF-LIBS) system that substantially improves the accuracy of elemental imaging on uneven material surfaces.¹

What is laser-induced breakdown spectroscopy (LIBS)?

LIBS is an elemental analysis technique that uses a short, high-energy laser pulse to ablate a small amount of material and generate a high-temperature plasma on the sample surface.² As the plasma cools, it emits light at characteristic wavelengths that serve as a unique spectral fingerprint for each element, allowing scientists to identify and quantify a sample's composition.² The emitted light is collected and analyzed by a spectrometer, with multivariate data analysis or calibration-free methods often used for complex or unknown samples.²

What were the benefits of using the AF-LIBS system introduced in the study?

One limitation in LIBS imaging is that it is susceptible to signal loss caused by defocusing when scanning surfaces with varying height.¹ In their study, the researchers developed an AF-LIBS system to address this limitation.

The results achieved encouraging results. In tests on samples with height variations of approximately 26 millimeters, the new method reduced the relative standard deviation of characteristic spectral line intensities to below 9.65% within targeted regions of interest, and improved spectral signal stability by a factor of 8.12 compared with conventional static nanosecond-LIBS imaging.¹

LIBS is widely used to map the distribution of chemical elements across material surfaces by firing a laser pulse to generate plasma, then analyzing the resulting light spectrum. The technique works reliably on flat samples, but conventional static systems struggle with irregular or contoured surfaces.¹ However, the beam falls out of focus as the laser-to-sample distance changes, and this is a challenge when it is an uneven surface. The result is that the plasma excitation is weakened and the signal-to-noise ratio is severely degraded.¹

Despite an assortment of solutions tested, none of them have solved the main challenge using LIBS imaging on uneven sources. Both hardware and software solutions were tried, but more difficulties were encountered when both methods were tried. On the hardware side, precision displacement platforms were used to physically reposition samples, but the issue with these platforms is that they are mechanically complex and lead to slow throughput.¹ On the software side of things, numerical compensation algorithms attempted to correct for signal loss, but they could restore the analytical precision lost when the plasma excitation itself became unstable.¹

What was the researchers’ solution and why did it work?

The research team sought to accomplish real-time focal tracking. This meant targeting the problem at the source rather than compensating and adjusting for it after. Their AF-LIBS system integrates a motor-driven focusing mirror module with synchronous height-sensing and focus-control logic, allowing it to track surface elevation changes in real time and adjust the laser's focal position accordingly.¹ According to the study, the system maintained a focus-tracking accuracy of ±0.1 millimeter during scanning, keeping plasma excitation conditions stable even as surface topography varied.¹

To test their method, the researchers designed experiments on samples with pronounced surface irregularity and applied a zoning strategy. The results showed that within these regions, spectral signal variability dropped sharply relative to static-focus imaging, and overall signal stability improved more than eightfold.¹

What are the main takeaways from this study?

The main takeaway that should be taken from this study is that the authors believe their results show that AF-LIBS can potentially be a viable technique for quantitative elemental imaging on complex surfaces.¹

“This study successfully developed and validated a LIBS imaging system incorporating dynamic real-time autofocus technology, effectively addressing the defocusing effect issue during element scanning on irregular material surfaces,” the authors concluded in their study.¹

References

1. Zhao, S.; Wu, J.; Li, Z.; Xu, X.; Dai, Y.; Zha, H.; Ni, Y.; Liu, Z.; Gao, X. Enhancing Elemental Visualization Imaging Accuracy on Irregular Material Surfaces with an Auto-focus Laser-induced Breakdown Spectroscopy Optical System. Talanta 2026, 307, 129797. DOI: 10.1016/j.talanta.2026.129797
2. Avantes, Laser-Induced Breakdown Spectroscopy Applications in the Physical Sciences. Avantes, 2026. https://www.avantes.com/applications/cases/laser-induced-breakdown-spectroscopy-applications-in-the-physical-sciences/ (accessed July 9, 2026).