LIBC Remote Sensing System Design And Primary Experiment Results

Laser Induced Breakdown Spectroscopy (LIBS) is a thriving material analysis technique. This technique has characters of no sample preparation, multi-element de-tection, and can achieve real time and in situ analysis, quick measurement, remote sensing. Therefore, LIBS has being widely applied in industrial metallurgy, space ex-ploration, environment monitoring and explosive inspection.The equipment of LIBS applied in industrial metallurgy can be grouped to two categories:immersion measurement system and telescope measurement system. Tele-scope,measurement system fits for measuring the melt metal in vacuum furnace, of which the laser focusing and plasma signal collecting optics is a key component. In this paper we set up an auto-focus LIBS remote sensing system for realizing LIBS non-contact measurement; system performance is tested by LIBS experiment in labor-atory environment. This LIBS remote sensing system not only fulfills the demand of industrial metallurgy real time analysis, but also can be used in other LIBS remote sensing field.The major work in this paper is summarized as follows:1. A auto focus telescope for LIBS remote sensing has been developed. The sample at any position in distance from1.5m to3.6m can be measured by the telescope. The exciting laser and the collected signal are transmitted in a same optical path, laying the foundation of the auto measurement of samples at different position. The telescope has an imaging module, which can take photos of the sample before and/or after the LIBS experiment, thus monitoring the burning spot caused by the laser ablation on the surface of solid sample.2. The relative position of the two spherical mirrors in the Schwarzschild optics is changed from homocentric to coaxial. The convex mirror is fixed on a computer con-trolled translation stage which can be moved. The focal length can be changed by ad-justing the distance between the two mirrors. The minimal distance change is5μm, accordingly the focusing length of about lmm. Compared with the optics in present LIBS remote sensing system, this telescope has a compact structure, easier to be man-ufactured and assembled.3. Auto focusing algorithm are investigated and tested. LIBS experiment has been conducted using copper sample in laboratory environment. Spectra lines of Cu are con-firmed. Control the convex mirror to move automatically and obtain spectrum data at different mirror spacing. Compare the maximal spectral intensities of spectral images of different position of the convex mirror and the mirror position correspond to the maximal spectral intensity can achieve the best focusing effect.The innovation of the work in this paper is:a LIBS remote sensing system is de-veloped; an auto-focus algorithm is designed for the system.