Abstract: A measurement system for indirectly measuring dimensions of a defect in a target area, within a range of working distances between the measurement system and the target area, the measurement system comprising illuminating optics for illuminating the target area, a laser pattern generator with a laser source and a pattern generating assembly for producing a reference laser pattern having at least one dimension essentially invariant within the range of working distances, the at least one dimension constituting a reference dimension in the target area, and projecting the reference laser pattern, alone a laser beam path, onto the target area, and an imaging system with imaging optics for obtaining an image of the target area together with the reference pattern, to determine the linear dimensions of the defect in the image relative to the reference dimension, wherein the laser beam path is spaced apart from the illuminating and imaging optics.