A microinterferometric method for analysis of rotation‐symmetric refractive‐index gradients in intact objects

SUMMARY A new method for measuring refractive‐index gradients in rotation‐symmetric objects is described. Interference micrographs of intact objects, with the symmetry axis perpendicular to the optical axis of the microscope, are used to obtain a phase‐shift profile, which is converted into a refractive‐index profile by a computer program. The conversion calculations are based on iterative approximations of the gradient slope in a number of presumed shells in the object. The method is fast, convenient and yields highly accurate results even when only a small number of phase shift values can be obtained. The new method is especially advantageous for analysing many invertebrate eyes but it can also be used for measuring manufactured graded‐index optical fibres.