Method for determining the refractive-index profile of a cylindrical optical object

A method for determining an index-of-refraction profile of an optical object, which has a cylindrical surface and a cylinder longitudinal axis, comprising the following method steps:

• (a) scanning the cylindrical surface of the object at a plurality of scanning locations by means of optical beams which are incident perpendicularly to the cylinder longitudinal axis;
• (b) capturing, by means of an optical detector, a location-dependent beam intensity distribution of the optical beams deflected in the optical object;
• (c) determining the angles of deflection of the zero-order beams for each scanning location from the intensity distribution, comprising eliminating beam intensities of higher-order beams from the intensity distribution so that an angle-of-deflection distribution is obtained for the zero-order beams and;
• (d) calculating the index-of-refraction profile of the object on the basis of the angle-of-deflection distribution,
• wherein method steps (a) and (b) are each carried out with light beams of different wavelengths, wherein a first location-dependent intensity distribution of a first light beam having a first wavelength and at least one further, second location-dependent intensity distribution of a second light beam having a second wavelength are obtained, and wherein the elimination of beam intensities of higher-order beams comprises a comparison of beam intensities of the first intensity distribution and of the second intensity distribution at the same scanning locations characterized in that for scanning the cylindrical surface according to method step (a), laser diodes with different emission wavelengths are combined via Y-fiber bundles to an optical beam, and wherein the optical beam is focused by means of a parabolic mirror.