MULTI-RESOLUTION IMAGE SIGNAL PROCESSING APPARATUS AND METHOD

摘要

An image signal processing architecture for image filtering using high and low image resolution scanning arrays to scan a document original. The image pixels produced by the high resolution scanning array are analyzed to determine the presence of high frequency halftone image pixels. Where high frequency halftone image pixels are not found, the image pixels are filtered to enhance the signal content and thereafter thresholded adaptively. Where high frequency halftone image pixels are determined to be present, the pixels produced by the low resolution array are descreened and thereafter rescreened at different screen frequency. A control switch permits the user to process continuous tone images directly. In the principal embodiment, both high and low resolution scanning arrays are disposed on a common substrate to form a unitary structure. In a second embodiment, separate scanning arrays are spaced at preset distances from the object plane to provide the requisite high and low image reading resolutions. To correlate image resolutions between the scanning arrays interpolation means are provided to interpolate additional image pixels in the output of the low resolution array.