Patent ID: 7308127

Claim:
A method to detect and analyze defects of a sample surface comprising: (a) exposing a surface to be investigated to collimated light and supplying radiation rejected therefrom to a position-resolving image processing means; (b) generating a mask on the basis of the image supplied by the image processing means, said mask having masked regions being defined by relatively bright areas of said image and unmasked regions being defined by relatively dark areas of said image, wherein a threshold value is determined in the gray level scale and image areas whose gray level values are below such threshold value are relatively bright areas and image areas whose gray level values are above such threshold value are relatively dark areas; and (c) exposing the surface to be investigated to diffuse light and supplying radiation rejected therefrom to the image processing means, with only the radiation from the unmasked regions being taken into consideration for setting illuminating conditions.