Abstract: The method of evaluating an optical defect in a transparent material includes irradiating the material with light to produce scattered light from the defect, rotating the material about a rotation axis passing through the defect, measuring scattered light intensity at a scattering angle (?s) to the rotation axis by means of a detector, determining the dependence of the measured scattered light intensity on rotation angle (?s) around the rotation axis and characterizing size and/or shape of the defect from that dependence. The apparatus for performing the method has a light source, a rotatable holder for the transparent material, a light sensitive receiving device and an imaging optical system for imaging scattered light from the material within a certain angular range on a detector surface of the receiving device.

Abstract: The method for determining local structures in optical materials, especially crystals, includes observing schlieren visually in a material to be tested with divergent white light in a first step; measuring birefringence of polarized laser light in the material to determine local defects and structure faults in the material with a spatial resolution of 0.5 mm or better in a second step if the material is judged to be suitable in the first step and then interferometrically measuring the material to determine the faults in the material by interferometry in a third step if the material is judged to be suitable in the first and second steps. This method can be part of a method for making optical components, especially for microlithography.

Abstract: The method for determining local structures in optical materials, especially crystals, includes observing schlieren visually in a material to be tested with divergent white light in a first step; measuring birefringence of polarized laser light in the material to determine local defects and structure faults in the material with a spatial resolution of 0.5 mm or better in a second step if the material is judged to be suitable in the first step and then interferometrically measuring the material to determine the faults in the material by interferometry in a third step if the material is judged to be suitable in the first and second steps. This method can be part of a method for making optical components, especially for microlithography.