US Patent 7130039 Simultaneous multi-spot inspection and imaging

A compact and versatile multi-spot inspection imaging system employs an objective for focusing an array of radiation beams to a surface and a second reflective or refractive objective having a large numerical aperture for collecting scattered radiation from the array of illuminated spots. The scattered radiation from each illuminated spot is focused to a corresponding optical fiber channel so that information about a scattering may be conveyed to a corresponding detector in a remote detector array for processing. For patterned surface inspection, a cross-shaped filter is rotated along with the surface to reduce the effects of diffraction by Manhattan geometry. A spatial filter in the shape of an annular aperture may also be employed to reduce scattering from patterns such as arrays on the surface. In another embodiment, different portions of the same objective may be used for focusing the illumination beams onto the surface and for collecting the scattered radiation from the illuminated spots simultaneously. In another embodiment, a one-dimensional array of illumination beams are directed at an oblique angle to the surface to illuminate a line of illuminated spots at an angle to the plane of incidence. Radiation scattered from the spots are collected along directions perpendicular to the line of spots or in a double dark field configuration.