Automatic Adjustment of Background WHITE LEVEL
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
This article discloses an automatic adjustment of white and black limits in a dynamic threshold technology in which both the white and black limits should be set to values to reduce undesirable black dots in the white background and white dots in the black background. The automatic adjustment is performed by detecting average levels of a real white area and a real black area and setting both limits at levels which are separated from the detected levels, respectively. Manual setting was proposed, but it had the disadvantage of reducing the dynamic range for the analog signal. A threshold level, to which one pel signal from an image scanner is compared, is determined by averaging plural pel signals, e.g., a 3 x 3 pel matrix surrounding the one pel. Fig.