1. An image recognition apparatus comprising an image extraction module for using an extraction window having a predetermined specified size to successively extract a plurality of partial images from an input image, such that said partial images extend entirely over said input image, and a judgement value calculation module for calculating respective judgement values corresponding to said partial images that are extracted by said partial image extraction module, each of said judgement values expressing a degree of probability that the corresponding partial image is a recognition-objective image having predetermined characterizing main features, wherein a partial image for which the corresponding judgement value calculated by said judgement value calculation module is a maximum (among the judgement values obtained for all of the partial images) is classified as being said recognition-objective image by said image recognition apparatus; wherein said judgement value calculation module comprises a discrimination module comprising a plurality of weak classifiers corresponding to respective images having different specific patterns, each weak classifier outputting a value 1 when it is judged that an input image is said recognition-objective image and outputting a value 0 when it is judged that the input image is not said recognition-objective image, a classifier selection module for appropriately selecting a weak classifier of said classifier selection module, to be applied to an object image which has been extracted as a partial image by said image extraction module, a likelihood value calculation module functioning, each time that a weak classifier is selected by said classifier selection module, to obtain a likelihood value, said likelihood value being calculated by multiplying a result value obtained by applying said selected weak classifier to said object image by a weighting value, said weighting value being predetermined as corresponding to said selected weak classifier, a cumulative likelihood value calculation module for cumulatively adding said likelihood values obtained by said likelihood value calculation module, to obtain a cumulative likelihood value, an expected likelihood value calculation module for calculating a positive judgement expectation value as a total of respective output values which would be produced, if the object image were judged to be the recognition-objective image, by all of those weak classifiers that have not yet been applied to said object image, and adding said positive judgement expectation value to said cumulative likelihood value to thereby obtain an expected likelihood value corresponding to the object image, and a continuation control module for judging whether said expected likelihood value exceeds a predetermined continuation threshold value, and when said continuation threshold value is exceeded, causing said classifier selection module to select a next one of said weak classifiers, while, if there is no succeeding weak classifier to be selected or said expected likelihood value does not exceed said continuation threshold value, said continuation control module terminates the processing of said object image and outputs said cumulative likelihood value calculated by said cumulative likelihood value calculation module as said judgement value corresponding to the object image.