Surface inspecting apparatus and method therefor

A method for inspecting a surface of an object, for use in a surface inspecting apparatus, comprising the steps of:

• a) obtaining a magnitude of an intensity gradient and an orientation of the intensity gradient of each pixel in an image of the surface by using a gradient operator;
• b) obtaining a symmetry magnitude map by using the magnitude of the intensity gradient and the orientation of the intensity gradient of each pixel, wherein the symmetry magnitude map exhibits the internal symmetry feature of a spot or contaminant on the surface;
• and
• c) detecting the spot or contaminant by using the symmetry magnitude map,
• wherein said step a) includes the steps of:
• a-1) inputting the image of the surface of the object;
• a-2) obtaining the magnitude of the intensity gradient by taking root mean square of the first intensity difference value between a reference pixel and a side adjacent pixel neighboring the reference pixel to obtain a first vector and the second intensity difference value between the reference pixel and an upper or lower adjacent pixel;
• neighboring the reference pixel to obtain a second vector and
• a-3) obtaining the orientation of the intensity gradient by taking orientation of a new vector produced by multiplying said two vectors, each representing the first intensity difference value and the second intensity difference value, respectively.

A computer-readable recording medium for storing a program implementing a method for inspecting a surface of an object in an apparatus having a large capability processor the method comprising the steps of:

• a) obtaining a magnitude of an intensity gradient and an orientation of an intensity gradient for each pixel of an image of the surface by using a gradient operator on the image;
• b) obtaining symmetry magnitude map exhibiting symmetry feature of a spot or contaminant by using the magnitude of the intensity gradient and the orientation of the intensity gradient;
• and
• c) detecting the spot or contaminant by using the symmetry magnitude map,
• wherein said step a) includes the steps of:
• a-1) inputting the image of the surface of the object;
• a-2) obtaining the magnitude of the intensity gradient by taking root mean square of the first intensity difference value between a reference pixel and a side adjacent pixel neighboring the reference pixel to obtain a first vector and the second intensity difference value between the reference pixel and an upper or lower adjacent pixel;
• neighboring the reference pixel to obtain a second vector and
• a-3) obtaining the orientation of the intensity gradient by taking orientation of a new vector produced by multiplying said two vectors, each representing the first intensity difference value and the second intensity difference value, respectively.