虹彩端の陰影変化を用いた虹彩認証のための生体検知法

摘要

A novel liveness detection method using the shadow around the iris edge depending on the directions of near-infrared illumination is developed. Iris recognition system is vulnerable to deception by fake irises although iris recognition is the most reliable method in biometrics. To overcome such a problem, various liveness detection methods have been proposed: the fast Fourier spectrum method, corneal reflection method, etc. However, these liveness detection methods accept an imposter as a legitimate person by using simple methods with a printed iris image. In this study, to develop the novel liveness detection method, the brightness variation in the iris edge was investigated by changing the direction of near-infrared illuminations. From the experimental results, the suitable combinations of the directions of near-infrared illuminations were 0°, 45° and 75°. The brightness variation rates were calculated between 0° and 45° as f_(avg)~(45), and between 0° and 75° as f_(avg)~(45) The f_(avg)~(45) in the live iris was between 4.63% and 18.23%. While, the f_(avg)~(75) in the live iris was over 18.23%. For the fake iris, on the other hand, the brightness variation rates for both f_(avg)~(45) and f_(avg)~(75) were less than 3%. Thus, the fake iris can be detected by using the difference of brightness variation rates between the live and fake irises.%近年，実用化が進む生体認証の問題の1つになりすましがある．この問題に対応するために，取得した情報が生体からのものか偽造によるものかを識別する生体検知法が開発されている．虹彩認証でも様々な生体検知法が提案されているが，印刷画像を用いた比較的簡便な方法によりなりすましが可能であるという報告がある．そこで本研究では，照射方向の異なる近赤外照明をランダムに点灯させ，近赤外照明の照射方向に応じて生じる虹彩端の陰影変化を利用した生体検知法を開発した．本提案法は，生体特有の変化を誘起させる刺激をランダムに呈示し，かつ，個人を識別するために用いる生体特徴情報と生体と偽造を識別するために用いる生体検知情報を同時かつ同一部位から取得できるため，なりすましが非常に困難な手法である．本研究では，生体と偽造を識別するための適切な近赤外照明の照射方向，虹彩領域，判定闇値について調査した．実験結果より，生体検知には0°，45°，75°の照射方向が適しており，生体と偽造を識別するための輝度変化の閥値は4．63％，生体確証のための輝度変化の闇値は18．23％であることを示した．