Method and apparatus for detection of target object with improved robustness

An object detection apparatus for detecting a presence of a target object in prescribed target areas on a target image taken from a fixed camera position, comprising:

• camera means, located at said fixed camera position, for taking the target image, a reference image in which the target object is known to be absent, and training images taken in which the target object is known to be present;
• feature calculation means for calculating features for the target image taken by the camera means, the features including at least one of a quantity expressing a difference of contributions by principal axis components and secondary axis components in a distribution of brightness of corresponding points in each target area on the target image and the reference image, and a quantity expressing a difference between a direction of a principal axis with respect to a vector (1, 1) direction in the distribution of brightness of corresponding points in each target area on the target image and the reference image;
• training means for training a classifier to classify the features calculated by the feature calculation means into those corresponding to a presence of the target object and those corresponding to an absence of the target object, by applying a training process using the training images taken by the camera means;
• classifier means for classifying the features calculated by the feature calculation means into a first class corresponding to a presence of the target object and a second class corresponding to an absence of the target object by using the classifier trained by the training means;
• and
• output means for outputting a detection result indicating the presence of the target object in the prescribed target areas on the target image taken by the camera means when the features for the target image calculated by the feature calculation means are classified into the first class by the classifier means, and the absence of the target object in the prescribed target areas on the target image taken by the camera means when the features for the target image calculated by the feature calculation means are classified into the second class by the classifier means.