Method for improving the contrast reproduction of digitized images

Method for contrast control for images which are to be recorded digitally, by using an electronic image sensor/scanner, which comprises the light-sensitive pixels of an active pixel image scanner (“AP”) whose effective sensitivity can be programmed individually, and whose sensitivity is varied to produce an image data record of an original that is to be imaged, (referred to as the “mask” herein) as a function of the brightness levels of an image data record of the original which comprises selected local frequency bands, characterized in that;

• an initial data record is produced from the original on the AP image sensor and is to be used for calculation of the associated mask, in which case the pixel sensitivity is intended to be distributed roughly homogeneously;
• in that the data record obtained in this way is passed (after being converted into a mask by computer means) to the AP image sensor preferably in the form of a mask normalized with respect to its average value;
• in that, to produce the improved data record of the original on the AP image sensor, the sensitivity of its individual pixels is reprogrammed, before exposure, in such a manner that—in the case of a positive mask—the sensitivity of the pixels is reduced in comparison with the mean sensitivity where the mask data record of the original has areas which are brighter than the average and as a function of a threshold which can be predetermined, and/or the sensitivity of the pixels is increased in comparison with the mean sensitivity where, in a corresponding manner, the mask data record of the original has darker areas;
• and
• in that the procedure when processing with a negative mask corresponds to this, but in the opposite sense.