Each Lens has it's own unique aberrations, - the further from the center of the lens the more aberration there usually is.
Image on the right demonstrates the lens aberrations.
In photography it is most important to have good resolution in the center of the photograph, but in panoramic applications we need the image to be uniform.
By taking the image of the pattern and comparing it to the ideal pattern we can determine point spread function of the lens and then use this function to correct aberrations in the post-processing of the images.
Image processing is performed by Java plug-in for ImageJ (Open Source Image processing program), which is a popular program for image processing in medical imaging, astronomy, etc.