Experimental Alignment Using Reverse-Path Laser Imaging

Abstract

In many research laboratories, modular spectrometric components are used. If experiments are often changed, alignment can be time consuming and difficult. In our atomic emission spectrometry (AES) laboratory, the light source and the spectrometer are not physically connected together, and the spectrometer is mobile—which necessitates frequent checking of the focusing and the alignment of the system. Previously we used a lens to collect light from our inductively coupled plasma for AES experiments. The focusing and alignment had been done by observing the plasma image on the entrance slit. While this approach is visually appealing, chromatic aberrations will inevitably cause defocusing in the ultraviolet region of the spectrum, and it is critical that we be able to image properly in this region. Recently we switched to the use of an off-axis concave mirror to eliminate chromatic aberrations caused by the use of the lens. It became evident during the design phase of this conversion that alignment would become more challenging due to the off-axis arrangement required by this configuration (Fig. 1).