Showing papers on "Watermark published in 1993"

High value documents

Abstract: A means of identification or document of value which includes a paper or polymer region, in particular, bank notes, passports, identification cards or any other document of sufficient value to make it liable to be copied or counterfeited, includes a watermark in the region and a liquid crystal material applied to the region and to at least a part of the watermark to produce optical effects which differ when viewed in transmitted and reflected light.

Detection of marks repetitively placed at lengthwise intervals along a web

Abstract: A system is disclosed for detecting watermarks or other marks made along a web of paper at regular intervals. The watermarks are detected by a video camera activated by a frame grabbing pulse in a control loop. The video for each frame grab pulse signal is digitized and processed to detect the watermark and to measure its position within the frame. The error between the measured position and a frame reference is used to adjust the value of a parameter (NEWCOUNT) representing the distance or pitch between successive watermarks. This value is in turn used to determine the moment of the next or a succeeding frame grab pulse. All timing is done in terms of measured length of web run by measuring pulses from an encoder. The control loop acts to track variations in the watermark pitch. The system may include circuitry for detecting and measuring every Mth mark while at the same time generating an interpolated pulse for each watermark usable in the control of a machine for cutting sheets of stationery paper from the web. Procedures are also described for automatically acquiring initial detection of watermarks on running the web up to speed. A fast infra-red strobe apparatus cooperable with the camera is also described as a source for illuminating the web.

Method of producing watermark paper

Abstract: A method of producing watermark paper comprising forming a patterned wire by fixing and bonding a lace to a cloth wire for papermaking, fitting this patterned wire to a cylinder mould of a cylinder-vat machine or a dandy roll as a face wire, and making paper by using the cylinder mould or the dandy roll to which the patterned wire is fitted. This method can easily and economically produce watermark paper having a delicate and complicated lace pattern in excellent gradation.