1. A method to reduce false alarms in identifying whether a candidate image is from an object class comprising: generating an object class subspace using principal component analysis on images of objects from the object class; generating a non-object class subspace using principal component analysis on images determined to be false positives of objects from the object class; projecting the candidate image onto the object class subspace; projecting the candidate image onto the non-object class subspace; removing similar principal components from each subspace so that each subspace is disjoint from each other before projecting the candidate image onto the object class subspace and projecting the candidate image onto the non-object class subspace; and determining whether the candidate image is from the object class using a Bayesian decision function based on the projecting of the candidate image onto the object class subspace and the projecting of the candidate image onto the non-object class subspace.