An image scanner for reading images from an original document or the like less susceptible to induced noise. An image output signal from a CCD sensor is sampled and held and the black level of the resulting signal is adjusted to a desired value. The black-level-adjusted signal is converted to digital...http://www.google.com/patents/US4907084?utm_source=gb-gplus-sharePatent US4907084 - Image reading unit with black level control
