New method for measuring the distribution of refractive index in blanks for GRIN optical elements

Characterization of refractive index distribution in optical materials is an important problem in the fabrication of glass blanks for GRIN optical elements. Most of the existing methods for such characterization have different disadvantages. For example, all methods of deviated beam depend on the accuracy of the distance measurements which are always limited by the radius of the laser beam scanning along the sample. Interference methods based on using a Mach-Zehnder interferometer can be used only for optical materials with small gradients of refractive index because of resolution limitations. Their disadvantage is also sensitivity to vibrations and temperature variations decreasing the accuracy of measurements.