Image correction method
View Patent ↗An image correction method having a small number of setting parameters achieved by integrating shift (alignment) in unit of a sub-pixel and image correction. A relationship between an inspection reference pattern image and a pattern image under test is identified, a mathematical expression model which fits a pixel error, expansion and contraction/distortion noise, and sensing noise of the image is constructed, and the model is simulated to generate an estimation model image.
1. An image correction method for generating an estimation model image from an inspection reference pattern image and a pattern image under test, said method comprising:
setting reference points at a plurality of separated positions of the inspection reference pattern image, giving weights to the inspection reference pattern image with reference to the reference points, and generating decomposed images the number of which is equal to the number of reference points;
generating simultaneous equations which describe an input-output relationship using a linear prediction model using, as an output, respective pixels of the pattern image under test and using, as an input, a linear coupling of a pixel group around pixel corresponding to each pixel of the decomposed images the number of which is equal to the number of reference points;
solving the simultaneous equations to estimate parameters of the prediction model; and
generating an estimation model image by using the estimated parameters.
2. The image correction method according to claim 1 , wherein
the linear prediction model is a two-dimensional prediction model using each pixel of the pattern image under test as two-dimensional output data and using a linear coupling of a pixel group around each pixel as two-dimensional input data.
3. The image correction method according to claim 1 , wherein
the parameters of the prediction model are estimated by using the least-square method.
4. The image correction method according to claim 1 , wherein
the reference points are apexes of the inspection reference pattern image or point near the apexes.
5. The image correction method according to claim 1 , wherein
the pixel group around the corresponding pixel is a pixel group of a 5×5 matrix arranged around the corresponding pixel.
6. The image correction method according to claim 1 , wherein
the linear coupling is performed by linear interpolation with respect to decomposed images the number of which is equal to the number of reference points.
7. The image correction method according to claim 1 , comprising
dividing the inspection reference pattern image and the pattern image under test into plurality of regions, respectively, before the decomposed image generating step, and wherein
parameters of the prediction model are estimated with respect to the divided images to generate an estimation model image.