Patent ID: 7492451
Filing Date: 2009-02-17
Classification: G01N

Abstract:
1. A method for detecting anomalies of a surface with a diffracting pattern thereon, comprising: focusing illumination beams of radiation to an array of spots on the surface; imaging scattered radiation from said spots onto an array of receivers or detectors, so that each receiver or detector in the array receives scattered radiation from a corresponding spot in the array of spots; causing relative rotational motion between the surface and the illumination beams so that the beams scan over an area of the surface; and wherein said imaging comprises causing scattered radiation from the array of spots to be passed to the array of receivers or detectors by means of a filter having an aperture that moves substantially in synchronism with the rotational motion to reduce diffraction from the pattern that is passed to the array of receivers or detectors as a result of the relative rotational motion between the pattern and the beams.