Optical fibers for scanning digitizers

Automated graphic activities such as computer cartography and computer-aided design require document-scanning systems that are stable, fast, and capable of handling large drawings and maps. In such a system the scanning assembly should accept documents readily and be compact and inexpensive enough to encourage wide usage. An attractive method for such automatic scanning and digitizing of engineering drawings combines optical fibers with a solid-state imaging array and a stepped friction feed. In this paper we describe an assembly of these elements employing a light-guide illuminator and receiver that are in direct contact with the drawing. Light signals, modulated by the dark areas on the drawing, are transmitted from the linear end of the lightguide to a grid configuration at the opposite end. The signals are optically coupled to and detected by a solid-state array sensor that scans the grid of optical fibers. The dimensional control necessary for fabricating the fiber grid to match the configuration of the solid-state array is critically important for the operation of this type of scanner. We therefore emphasize in this paper the dimensional requirements for the glass fiber assembly, the signals detection, and the accuracy of scanning.