8. The object detection apparatus according to claim 1 , wherein the search unit searches the image in a predetermined search window size changing amount, the predetermined search window size changing amount being determined by searching a plurality of sample images m containing the object while a size of the search window is changed, comparing the sample images in the search window with the dictionary, counting a detection frequency in a direction parallel to a road plane to thereby produce histograms, calculating maximum search window size changing amount based on a maximum detection frequency in the histograms for each search window size, and averaging the maximum search window size changing amounts derived for the plurality of sample images m to obtain an average maximum search window size changing value that serves as an upper limit of the predetermined search window size changing amount.
8. The object detection apparatus according to claim 1 , wherein the search unit searches the image in a predetermined search window size changing amount, the predetermined search window size changing amount being determined by searching a plurality of sample images m containing the object while a size of the search window is changed, comparing the sample images in the search window with the dictionary, counting a detection frequency in a direction parallel to a road plane to thereby produce histograms, calculating maximum search window size changing amount based on a maximum detection frequency in the histograms for each search window size, and averaging the maximum search window size changing amounts derived for the plurality of sample images m to obtain an average maximum search window size changing value that serves as an upper limit of the predetermined search window size changing amount. 9. The object detection apparatus according to claim 8 , wherein a graph is produced such that one axis represents the size of the search window and the other axis represents the maximum detection frequency, and a width of a peak of the graph is determined as the maximum size changing amount.