Optical scanning - using reference points to allow for distortion of screened original

摘要

The optical scanning of a screened original, to derive control data for a printer or plotter or textile working appts., uses a plate or drum (9) to support the original (1). The screen size and the screen points per line are either inserted manually through a keyboard or selected from a menu pref. from a VDU connected to a process computer with a memory holding standard screen data for access. The inserted or selected screen data for the original (1) are used by the process computer to start the scanning process, using screen points as reference points. The original is divided according to the reference points and the screen size so that the scanner (4) can scan the original (1) according to the internal computer screening, in spite of the actual position and distortion at the original. The co-ordinates of the scanned image points on one side, and the image point data on the other side are digitised and stored. ADVANTAGE - The method gives a trouble-free optical scanning of screened originals which are not accurately positioned or are distorted, to give the control data for a dot-for-dot reproduction.