To remove the effects of rigid head motion, perspective alignment is used. Three examples are shown below. In each, Row A shows the original image sequence. Row B shows the intensity differences between the initial image in Row A and each subsequent image. Areas of white indicate rigid and non-rigid motion. For instance, B5 is the difference between A5 and A1; B10 is the difference between A10 and A1. Row C shows the results of a perspective alignment of the image sequence in Row A. Row D shows the corresponding difference images. After perspective alignment, rigid motion is absent.
