Repeatability improvement of laser-induced breakdown spectroscopy using an auto-focus system

Abstract

Laser-induced breakdown spectroscopy (LIBS) is a novel technique for elemental analysis of materials. The repeatability of LIBS results is an important issue in many applications. Many factors influence the repeatability of LIBS results. The aim of this study is to examine the effect of laser beam focusing position or lens to sample distance (LTSD) as one of the most important factors influencing LIBS spectra. A point auto-focus system is designed and applied to provide the same lens to sample distance in every LIBS experiment. This system is employed and the result is compared to that of non-auto-focus technique on samples with different degrees of evenness such as aluminum, paper, tape and human fingernail. The standard deviation of this experiment is measured in the range of 4 to 26 μm. Then, spectrum’s repeatability is examined with two samples of aluminum and human fingernail. The standard deviation of spectra is considerably reduced. In conclusion, repeatability of LIBS results could be optimized by using the auto-focus system.