Qinetiq Limited

Quinetiq Limited

George Jiri Tomka

Jonathan Geoffrey Gore

Christopher Robert Lawrence

Mark Gregory Maylin

Stuart John Eaton

Adam Daykin

James Carl Milne

In order to check the authenticity of a banknote or other such document it is printed with two patches of magnetisable ink, and each patch is magnetised to present a multipole sequence of alternating polarity. If the document is folded to bring the two patches together and then rubbed to and fro in the direction of the pole sequences, they will be subject to alternating forces of attraction and repulsion which can be sensed through the fingertips and gives the impression of a physically rippled texture notwithstanding that the patches actually have a smooth surface. The presence or absence of this effect can therefore be used to distinguish between a genuine document bearing such magnetised patches and a counterfeit which may be visually identical but lacks the correct magnetisation. In a variant only one of the patches is printed on the document itself and the other is on a separate 'key' device which is rubbed over it to test for the presence of the correct magnetisation.

Documentation authentication

A stress or magnetic field sensor comprising a generally elongate magnetically soft amorphous or nanocrystalline electrically resistive element and biasing means for applying to the element a bias magnetic field of which the component directed along the length of the sensor has an amplitude variation pattern along the element. A periodically varying pattern has the effect of reducing the sensitivity of a stress sensor to external ambient fields (FIG.shows that with a sawtooth bias field the sensitive portions a of a sensor move to positions b in the presence of an ambient field, but their number remains the same). A ramped bias field enables the position of the sensitive region of the sensor to be controlled, for measuring local stress, or for mapping an external magnetic field. Control of the regions where the sensor is active may include selective conductive coating of portions of its length. Potential uses of the stress sensor include a pressure sensor, embedment in moving parts (using rf communication) such as vehicle tyres, aircraft wings or machine parts, and in structures such as bridges where stray magnetic fields are a problem.

Stress or magnetic field sensor with spatially varying bias

Growing community of inventors

Greenham, United Kingdom

George Jiri Tomka