Surface inspection method and apparatus

A method of inspecting a surface of a thing, in which a surface condition of a thing to be inspected is inspected on the basis of detection signals from an optical sensor having a plurality of detecting portions arranged in the sub-scan direction, each of said detection signals corresponding to intensity of scattering light obtained by X-Y scanning the thing to be inspected with a laser beam making a predetermined angle with respect to a surface of the thing in one of X and Y direction as a main scan direction and the other as a sub-scan direction, said surface inspection method comprising:

• a map acquisition step of obtaining a map of levels equal to a level of the image of the point-source light by using a measuring device comprising a light source optical system for focusing an image of a point-source light in a focal point of a detection optical system lens unit, a light receiving unit, a measuring optical system including said detection optical system lens unit detachably coupled thereto with an optical axis of the measuring optical system is aligned with an optical axis of said detection optical system lens unit, for focusing the image of the point-source of light from said detection optical system lens unit in a light receiving surface of said light receiving unit, a first moving means for moving the measuring optical system along said optical axis of said measuring optical system, a second moving means for linearly moving said measuring optical system in a direction perpendicular to the optical axis of said measuring optical system and a mathematical operation processor for obtaining a level of the image of said point-source light obtained from said light receiving unit together with 2-dimensional coordinates of respective measuring points by 2-dimensionally moving said measuring optical system by said first and second moving means and for outputting data of levels of light from the respective measuring points, which are the same as the level of the image of said point-source light;
• an angle acquisition step of obtaining an angle of the light receiving direction in which the shading effect of the lens of the detection optical system in the plane perpendicular to the optical axis of the measuring optical system is minimum from the map;
• and
• a step of making a relation between the detection optical system lens and the optical sensor a state where they are rotated by a setting angle in a light receiving direction in which shading is minimum, wherein the surface condition is inspected on the basis of the level of the detection signal.