Patent ID: 8239163

Claim:
Apparatus for determining surface structure element characteristics, wherein the apparatus comprises a data processor, the data processor comprising a structure determiner: wherein the structure determiner includes: an intensity data storage for holding: a) structure intensity data comprising a first series of intensity values resulting from a measurement operation by an interferometer on a surface structure sample area using an objective such that the spread of light from a light source of the interferometer at the sample surface is greater than a surface characteristic of surface structure elements of the surface structure sample area and b) non-structure intensity data comprising a second series of intensity values resulting from a measurement operation on a second sample surface area not having the surface structure; and a controller coupled to the data storage, the controller being configured to cause the structure determiner: to determine a transform ratio relating to a ratio between the structure intensity data and the non-structure intensity data; to determine values for surface characteristics of the surface structure sample area by applying the determined transform ratio to a relationship representing the structure of the surface structure sample area.