Patent ID: 8614790

Claim:
A method for use in optical inspection of patterned samples, the method comprising: selecting illumination and collection masks for locating in illumination and collection channels respectively, in conjugate planes, being spectral planes with respect to an inspection plane defined by a sample under inspection, wherein said selecting comprises: selecting first and second spatial patterns of features for the illumination and collection masks, in accordance with a known diffraction response from the sample under inspection to illumination by a given illumination spot, such that the first and second spatial patterns are formed by light transmitting and blocking regions, defining, respectively, a dimension of an illuminating spot and a numerical aperture of the illumination channel, and a dimension of a light collection region; providing a predetermined angular orientation of the illumination channel with respect to the inspection plane, and a predetermined angular orientation of the collection channel with respect to the inspection plane, thereby providing that light components of first structured light created by light passage through the illumination mask are in a predetermined alignment with spaces between light components of second structured light created by light passage through the collection mask, determining a desired relation between the collection region defined by the light components of the second structured light and the dimension of the illumination spot; illuminating a sample with light propagating through the illumination mask along the illumination channel having said numerical aperture and having said predetermined angular orientation with respect to an inspection plane, thereby creating the illuminating spot on the sample and causing the diffraction response from the sample; collecting light returned from the sample through the collection mask along the collection channel of the predetermined angular orientation with respect to the inspection plane and allow propagation of the collected light to a detection plane.