Pattern inspection apparatus and pattern outline position acquisition method

A pattern inspection apparatus comprising:

• an image acquisition mechanism configured to include an emission source to emit beams, a lens to focus the beams, and a detector to detect a beam intensity, and configured to acquire an image of a substrate on which a figure pattern has been formed;
• a filter processing circuit configured to perform, for each direction, filter processing on the image, using a plurality of two-dimensional spatial filter functions with different orientations;
• an outline pixel candidate extraction circuit configured to extract a plurality of pixels each having a predetermined value larger than a first threshold, in pixel values each for the each direction of after the filter processing, as a plurality of outline pixel candidates through which an outline of the figure pattern passes;
• an outline pixel extraction circuit configured to extract a plurality of outline pixels from the plurality of outline pixel candidates by excluding outline pixel candidates each of which has a differential value, greater than or equal to a second threshold, obtained by differentiating a pixel value of before the filter processing in a second direction orthogonal to a first direction corresponding to the predetermined value;
• an outline position calculation circuit configured to calculate, for each of the plurality of outline pixels, an outline position per sub-pixel, using a one-dimensional profile in the first direction corresponding to the predetermined value;
• and
• a comparison circuit configured to compare an outline of the image and a predetermined reference outline, based on data of the outline position.