METHODS AND APPARATUS FOR MONITORING ARTICLES

摘要

A method and apparatus for monitoring articles to determine the presence of an authenticity indicating characteristic. The method comprises irradiating an article with radiation in at least first and second wavebands; detecting first radiation generated by the article in response to irradiation at the first waveband, the first waveband being chosen such that the first radiation generated varies in accordance with the presence or absence of the authenticity indicating characteristic and in response to the presence of obscuring material on the article. Second radiation generated by the article in response to irradiation at the second waveband is detected, the second waveband being chosen such that the second radiation generated by the article varies with the degree of obscuring material on the article but is substantially independent of the presence of the authenticity indicating characteristic. The detected radiations are compared to determine whether or not the authenticity indicating characteristic is present.