1. A method for detecting certain objects in an image, comprising the computer-implemented steps of: placing a working window at different positions in an input image such that the input image is divided into a plurality of same dimension subwindows; providing a cascade of homogenous classification functions, each of the homogenous classification functions in sequence in the cascade respectively having increasing accuracy in identifying features associated with the certain objects; and for each subwindow, employing the cascade of homogenous classification functions to detect instances of the certain objects in the image.