Optical Non-Linearities in Infrared Mircospectroscopy: A Preliminary Study into the Effects of Sample Size and Shape on Photometric Accuracy

Abstract Several years ago this laboratory reported on the effects of stray light in an infrared microscope and its consequences on the spatial resolution achievable in a typical line scan or mapping experiment of a polymer film. In this study it was demonstrated that unless the size of the sampled area was greater than twice the wavelength of light employed for the analysis, a significant amount of stray light from near neighbors was contained in the sampled areas. Further, this generalization is only valid for sample sizes above the diffraction limit. The results of this study are summarized in Table. The ratio of the sampled area to that of the aperture size (corresponding to expected sample size) can be thought of as a degradation factor in spatial resolution. In this earlier study the sample geometry was chosen to minimize stray light effects arising from the sample size and shape.