Patent ID: 8174690

Claim:
An apparatus for optically characterizing a surface structure of a board or sheet, the apparatus comprising: a light source arranged at a first side of a said board and adapted to illuminate a first area of a surface of said board or sheet by emitting towards said surface a collimated light beam at a first, oblique angle of incidence relative to said surface of said board or sheet, wherein the light source comprises an optical collimator adapted to provide said light beam as a broad, collimated light beam having an elongated cross section of a first length, and propagating in a first plane, and the first plane is substantially perpendicular to a plane of said first part of said surface of said board or sheet, and wherein the first, oblique angle is such that the first length when projected onto the first surface is substantially equal to or greater than a width of said board or sheet; and a light receiver arranged at a second side of a said board or sheet, said second side being substantially opposite to said first side in respect of said board or sheet, said light receiver adapted to receive at least a part of said collimated light beam being reflected off said first area of said surface of said board or sheet, and including a spatial detector adapted to receive by different parts of said detector light of said collimated light beam being reflected off respective, different parts of said first area, wherein the detector is an image detector extending along an axis of extension lying in the first plane or a plane obtained by folding said first plane along a folding line, and wherein the axis of extension is angled different from a perpendicular to the optical axis, such that a proximal part of the first area of the surface being proximal to the light receiver is properly focused at corresponding first one end of the image detector and a distal part of the first area of the surface being distal to the light receiver is properly focused at corresponding second end of the image detector.