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.

Feasibility Study on Discrimination of Neo-plastic and Non-Neoplastic Gastric Tissues Using Spark Discharge Assisted Laser Induced Breakdown Spectroscopy

“…Emissions of excited atoms, ions, and molecules in this plasma are recorded as a spectrum and analyzed for atomic identification of the sample. In recent years, this technique is mostly used for analysis of different tissues, including hard tissues such as hair, 11 nails [12][13][14][15][16][17][18] and teeth [19][20][21][22] and soft tissues such as blood, 23 cervical, 24 liver 25 and colorectal tissues. 26 What sets this method apart from other conventional methods is the convenience of sample preparation, higher speed of performance and no direct connection with samples especially contaminant materials.…”

Accurate and Rapid Auto-Focus Methods Based on Image Quality Assessment for Telescope Observation

“…Applying the auto-focus principle above, the AFT of a Cassegrain telescope EOTS system was investigated, as shown in Figure 1. The EOTS system mainly consists of five parts [21]: Cassegrain telescope, CCD camera, PC control module, stepper motor, and mechanical conversion module. In the experiment, a Cassegrain telescope composed of a fold back mirror structure with two primary and secondary parabolic reflectors was used to collect the information of detected objects.…”

Classification of uneven steel samples by laser induced breakdown spectroscopy based on a Bessel beam

“…Maurice et al 18 realized autofocus by using a laser ranging system and successfully applied it to the ChemCam. By analyzing the spot offset of different focusing positions captured by a CCD, Ashrafkhani et al 19 realized a system with automatic focusing. Cortez et al 20 designed an optical system based on two laser pointers for autofocus.…”