Interferometric measurement of laser fusion targets

We describe techniques for the quantitative interferometric characterization of wall thickness variations of hollow glass microspheres. By using a combination of techniques, one can rapidly form a picture of the total configuration for most defect combinations. These techniques require only very simple calculations and do not involve detailed ray tracing through the sphere. We also show how ray tracing calculation can be done very simply for careful analysis of the interference phenomenon in a perfect sphere. These calculations show that if both a large illumination angle and a large aperture objective are used, the nonparallel illumination causes degradation of both the spatial and the phase resolution of the interferometer. These problems can be overcome by properly aperturing the illumination.