“…As a classic topic, numerous face detection systems have been proposed during the past decades or so. Existing face detection methods can be broadly categorized as handcrafted feature based methods [16,17,18,19] and CNN-based methods [20,21,10,11,22,23]. However, most of detection systems based on handcrafted features only train a single scale model, which is applied to each level of a feature pyramid, thus increasing the computation cost drastically, especially for the complicated features.…”