1. An image recognition apparatus for applying a recognition processing procedure to an input image to detect a recognition-subject image located within said input image, the apparatus comprising sub-image extraction circuitry configured to successively extract a plurality of sub-images from said input image, said plurality of sub-images covering all of said input image, recognition judgement value calculation circuitry configured to process a currently extracted sub-image, for calculating a recognition judgement value corresponding to said sub-image, said recognition judgement value being indicative of a probability that said sub-image corresponds to said recognition-subject image, and judgement circuitry configured to detect said recognition-subject image based upon said corresponding recognition judgement values of said sub-images; said recognition judgement value calculation circuitry comprising a plurality of weak classifiers configured for recognition of respectively different feature patterns of an image and having respective corresponding weights, each weak classifier configured to generate a decision value of 1 or 0 when applied to a sub-image, in accordance with whether or not recognition is achieved, selection circuitry configured to selectively apply said weak classifiers in sequence to said currently extracted sub-image as an object image, and likelihood calculation circuitry configured to multiply a decision value outputted from a currently selected one of said weak classifiers by a corresponding weight of said weak classifier, to obtain a value of likelihood; wherein said image recognition apparatus comprises: likelihood accumulation circuitry configured to calculate a cumulative likelihood as a total of said values of likelihood obtained up to a current point in said sequence; positive judgement expectation value calculation circuitry configured to calculate a positive judgement expectation value as a total of respective values of likelihood which would be generated by a pending set of said plurality of weak classifiers in the event that said object image corresponds to said recognition-subject image, said pending set comprising those of said plurality of weak classifiers which have not yet been applied up to said current point; expected likelihood calculation circuitry configured to calculate an expected likelihood as a sum of said positive judgement expectation value and said cumulative likelihood; and continuation control circuitry configured to respond to said expected likelihood becoming less than a predetermined threshold value by interrupting said sequence, and to output a currently obtained cumulative likelihood as said recognition judgement value corresponding to said currently extracted sub-image, at a time when said sequence becomes completed without interruption or becomes interrupted.