Image Number 12 for United States Patent #8130138.
A ghost target candidate judging device judges that one target of two targets is a candidate for a ghost target where the distances of the two targets from a subject vehicle are equal to each other and where the difference between receiving levels of the two targets is not less than a predetermined value. A running-abreast target judging device judges that one target is the target running abreast of the other target based on changes in an angle difference and in a left-right positional difference between the two targets in accordance with the change in the distances of the two targets from the subject vehicle. The ghost target judging device judges, as the ghost target, a target obtained by removing the running-abreast target data from the candidates for the ghost target. The running-abreast target is prevented from being erroneously recognized as the ghost target while judging which target is the ghost target. Also, a target indicating a lower receiving level is prevented from erroneously being judged as a ghost target when two targets indicating their respective different receiving levels are running side by side.