A simple method to obtain the fourth-order coefficient of the series expansion for the radial distribution of a lenslike medium is described. The coefficient is obtained by measuring the position of a discontinuity of the far-field intensity pattern. The relation between the coefficient and this position is calculated by using either the ray theory or the wave theory. By using a ray model, the position of the discontinuity and the macroscopic intensity distribution is easily obtained.
© 1978 Optical Society of America
Korehiro Maeda and Joji Hamasaki, "A method of determining the refractive index profile of a lenslike medium," J. Opt. Soc. Am. 67, 1672-1680 (1977)