1. A method for detecting a face, comprising: detecting a circle having a predetermined radius from an input image by using a Hough transform; dividing a region of the detected circle to form image fragments of the same size; generating input vectors for each of the image fragments by using each classifier of a cascade that includes homogeneous classifiers, wherein input vectors are calculated based on local binary descriptors and the local binary descriptors include a pairwise intensity comparison between a pixel and eight or fewer neighboring pixels; when an input vector generated for each of the image fragments is classified into a non-face type, determining that no face is detected in the input image; and when an input vector generated for each of the image fragments is classified into a face type by the classifier of the cascade, determining that a face is detected from the input image.