An image of an original document (16) is sensed to determine if the document (16) is a printed document (the image consists of characters and symbols) or a photographic document. The exposure illumination intensity, developing bias voltage and/or other variable operating parameters are controlled in...http://www.google.com.tw/patents/US4239374?utm_source=gb-gplus-share專利 US4239374 - Electrostatographic apparatus comprising automatic document type determination means
