Confocal Raman microscopy: common errors and artefacts

Confocal Raman microscopy is a powerful tool for research and analysis in the chemical, materials and life sciences, particularly for non-destructive depth profiling of transparent systems. Unfortunately, many Raman microscopes are not optimally configured for this purpose, and so yield unnecessarily low signal-to-noise spectra with poor spatial resolution and grossly incorrect depth scales. This review discusses the aberrations and artefacts that can arise and describes how these can be avoided by adhering to a few basic principles that are well known to optical microscopists but which were largely ignored in the spectroscopic community for many years.