Patent ID: 8150854

Claim:
An image search apparatus comprising: a processor, comprising: a dimension reducing unit that reduces dimensions of multidimensional feature data extracted from an image, to produce approximate data; an approximate-data storing unit including a memory that stores the approximate data produced by the dimension reducing unit corresponding to the multidimensional feature data used to produce the approximate data; a search request receiving unit that receives at least an identifier which identifies multidimensional feature data of a person to be searched, as a search key; an approximate-space searching unit that calculates distances from approximate data corresponding to the search key received by the search request receiving unit, to plural approximate data stored in the approximate-data storing unit, based on search conditions, and arranges the distances in order of similarity; and a real-space final ranking unit that performs a further distance calculation of distances from the multidimensional feature data used to produce the approximate data produced by the dimension reducing unit, to corresponding data of the search key, on a group of results in which the similarity obtained by the approximate-space searching unit is high, determines final rankings, and outputs the final rankings as a search result; wherein the real-space final ranking unit performs a distance recalculation using the multidimensional feature data used to produce the approximate data produced by the dimension reducing unit, in descending order of elements in which the similarity obtained by the approximate-space searching unit is high (i.e., in ascending order of the approximate distance), completes the process at a timing when top K pieces of actual distances which are obtained by the recalculation and in which the similarity is high are smaller than an approximate distance of all data that are not subjected to the distance recalculation, and outputs the top K pieces of distances as the search result.