Surface pit and mound detection and discrimination system and method

A surface pit and mound detection and discrimination system comprising:

• means for directing a beam of radiation to a surface;
• means for providing relative motion between said beam and the surface;
• means for separately sensing radiation scattered from the surface in the near-specular region and in the far-specular region for differentiating between pits and mounds, and other types of defects;
• sensor means for detecting reflected radiation from the surface in the near-specular region for determining any deviation of said reflected radiation from the path expected for a nominal surface, and for producing at least one signal representative of whether said beam directed to the surface is traversing the positive or negative slope of a defect on the surface;
• and
• means, responsive to said sensor means, for distinguishing whether said defect is a pit or a mound in response to a change of slope on the surface.

A method of detecting pits and mounds on a surface and discriminating between them, comprising:

• scanning a beam of radiation over a surface;
• separately sensing radiation scattered through the surface in the near-specular region and in the far-specular region for differentiating between pits and mounds, and other types of defects;
• detecting a local slope on the surface from radiation scattered from the surface in the near-specular region;
• and
• differentiating between whether said beam of radiation is scanning a pit or a mound.

A method of detecting pits and mounds on a surface and discriminating between them, comprising:

• directing a beam of radiation to a surface;
• providing relative motion between the beam and the surface;
• detecting reflected radiation from the surface including separately sensing radiation scattered from the surface in the near-specular region and in the far-specular region for differentiating between pits and mounds, and other types of defects;
• determining any deviation of the reflected radiation from radiation scattered from the surface in the near-specular region from the path expected for a nominal surface;
• producing a signal representative of whether the beam of radiation directed to the surface is traversing a positive or negative slope on the surface;
• and
• distinguishing whether the beam directed to the surface is traversing a pit or a mound in response to a change in slope on the surface.

A surface defect pit and mound detection and discrimination system comprising:

• means for scanning a beam of radiation over a surface;
• means for detecting a local slope on the surface including first and second detectors for sensing radiation reflected from the surface, each said detector disposed and masked for separately indicating a deviation in one direction from the path expected for a nominal surface representative of a local slope on the surface;
• and
• means, responsive to said means for detecting, for differentiating between whether said beam of radiation is scanning a pit or a mound.