Optical methods for monitoring the micro-geometry of a surface

Optical methods of checking for defects in the exterior part of an object on the basis of micro-geometric features and of the surface are considered by means of an analysis of the radiation reflected by the surface, where the information parameters of this radiation are related by means of a parameter Rq. The advantages in terms of the sensitivity of these optical methods over other methods are evaluated on the basis of a theorem proved in the present article. The theorem demonstrates that the mean values of the derivatives of the roughness parameters Rq and Ra depend on the length of the estimator.