Apparatus is provided for recording halftone dot images on a photosensitive material by emitting a light beam which is modulated in accordance with digital image data. In a screen pattern memory (23), screen pattern data provided with a value for each element area which is smaller than a light spot diameter...http://www.google.com.tw/patents/US4912568?utm_source=gb-gplus-share專利 US4912568 - Halftone dot image recording apparatus and method employing high density screen pattern signal for light beam modulation
