Patent ID: 8630453

Claim:
An image processing device comprising: an optical flow computation unit that computes optical flow only within a partial region of an image for multiple reference points within the partial region with reference to a past image; an optical flow detection unit that detects whether or not optical flow is generated at the reference points inside the partial region; a feature point data storage unit that stores as a feature point, when optical flow is generated at the reference points inside the partial region, a set of pixels of pixel data for the reference points in the partial region that generated the optical flow; a feature point tracking unit that tracks a motion position of the feature point for each frame in the partial region; a feature point deletion unit that deletes the tracked feature point in the partial region in accordance with a sudden variation in motion position of the feature point over frames relative to a group of feature points that move in a same direction within the partial region, wherein the feature point is deleted when it cannot be put into the group of feature points that move in the same direction within the partial region; and a passage determination unit that determines whether or not passage of an object is detected within the image based on a predetermined number of multiple remaining undeleted feature points moving together in the group in the same direction within the partial region.