Apparatus for scanning a moving object includes a visible waveband sensor
12 oriented to collect a series of images of the object as it passes
through a field of view 16. An image processor 14 uses the series of
images to form a composite image. The image processor 14 stores image
pixel data for a current image and a predecessor image in the series. It
uses information in the current image and its predecessor to analyse
images and derive likelihood measures indicating probabilities that
current image pixels correspond to parts of the object. The image
processor 14 estimates motion between the current image and its
predecessor from likelihood weighted pixels. It generates the composite
image from frames positioned according to respective estimates of object
image motion. Image motion may alternatively be detected by a speed
sensor such as a Doppler radar 200 sensing object motion directly and
providing image timing signals.