Document scanner and image processor - has reading unit and associated signal processor to create image data, with amplifier and interpolator including variable signal level control

The document scanner has a reading unit [1] which provides a signal input to a signal processor [5], and an input stage [52] generates image data signals. An amplifier and an interpolation circuit [102] provides input to a binary representation and image density conversion circuit [104]. The conversion unit is controlled by a variable signal level stage [103] to provide improved resolution of the image data. The determined data coefficients may be used before and after the picture data.