Real-time depth measurement for micro-holes drilled by lasers

Cheng Hsiang Lin, Rock A. Powell, Lan Jiang, Hai Xiao, Shean Jen Chen, Hai Lung Tsai*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)

Abstract

An optical system based on the confocal principle has been developed for real-time precision measurements of the depth of micro-holes during the laser drilling process. The capability of the measuring system is theoretically predicted by the Gaussian lens formula and experimentally validated to achieve a sensitivity of 0.5 νm. A nanosecond laser system was used to drill holes, and the hole depths were measured by the proposed measuring system and by the cut-and-polish method. The differences between these two measurements are found to be 5.0% for hole depths on the order of tens of microns and 11.2% for hundreds of microns. The discrepancies are caused mainly by the roughness of the bottom surface of the hole and by the existence of debris in the hole. This system can be easily implemented in a laser workstation for the fabrication of 3D microstructures.

Original languageEnglish
Article number025307
JournalMeasurement Science and Technology
Volume21
Issue number2
DOIs
Publication statusPublished - 2010

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