Abstract
Generally, a large-scale 2-D profile is obtained from the combination of a series of 1-D profiles measured by 1-D differential methods. These methods have the disadvantage that the results are affected by rolling error of the scanning stages. This paper presents some 2-D differential methods which can eliminate the datum errors including the translation error in the longitudinal direction and the pitching and rolling errors, and evaluates their basic characteristics in detail. The analysis shows that the asymmetric 2-D mixed method is superior to the others with respect to the spatial frequency resolution and the longitudinal resolution.
