Patent ID: 8514408

Claim:
An apparatus for measurement of a curvature of a surface ( 1 ), comprising: means adapted for irradiating a first light beam (S 1 ), a second light beam (S 2 ) and a third light beam (S 3 ) onto a surface ( 1 ) of a sample ( 12 ), wherein the first light beam (S 1 ), the second light beam (S 2 ) and the third light beam (S 3 ) are parallel to each other and the first light beam (S 1 ) is spaced apart from a plane defined be the second light beam (S 2 ) and the third light beam (S 3 ); a detector ( 5 ) comprising at least one detector plane and being adapted to detect a first position of the reflected first light beam (S 1 ) in the at least one detector plane, a second position of the reflected second light beam (S 2 ) in the at least one detector plane and a third position of the reflected third light beam (S 3 ) in the at least one detector plane; means adapted to determine a first distance between the first position of the first light beam (S 1 ) and the third position of the third light beam (S 3 ) and adapted to determine a second distance between the second position of the second light beam (S 2 ) and the third position of the third light beam (S 3 ); means adapted to determine a mean curvature of the surface ( 1 ) from the first distance and the second distance, and means adapted to determine a maximum azimuthal curvature deviation from the determined mean curvature.