Object-detection with a varying number of eigenspace projections

We present a method allowing a signiicant speed-up of the eigen-detection method (detection based on principle component analysis). We derive a formula for an upper bound on the class-conditional probability (or, equivalently, a lower bound on the Mahalanobis distance) on which detection is based. Often, the lower bound of Mahalanobis distance (MD) reaches a preset threshold after computation of only a few eigen-projections. In this case the computation of MD can be immediately terminated. Regardless of the precise value of MD, the detection hypothesis (object from class is detected) can be rejected. While provably obtaining results identical to the standard technique, we achieved a two to threefold speed-up in face detection experiments on images from the CMU database.