NEW YORK — Ralph Lauren is a busy man. At the moment, for example, he has just opened his early fall signature collection, along with his fall sport and bridge lines. Then, of course, there’s the little matter of that IPO, expected this spring. But all this activity hasn’t altered his devotion to the classics. For fall, his looks range from traditional glen plaid jackets worn with leather pants and dog collars to the sleekest of sport shapes. Here, some of the best.