AN AUTOFOCUS SYSTEM FOR REPRODUCIBLE FOCUSING IN LASER-ABLATION INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

A method of controlling the focus position of the ablating laser was e valuated. This system consists of a displacement measuring unit based on the triangulation displacement measurement principle. A simple prel iminary experimental setup with a light source (LED, light emitting di ode) and a displacement sensor (PSD, position sensing detector) with o ptics and a electronic circuit, resulted in a reproducibility of a giv en lateral position of +/-5 mu m. A fine-tuning of the components, as well as the use of a laser diode as a light source wilt certainty impr ove this value.