Kazuo FUJIWARA^1,2 and Osamu MATOBA²

¹Research and Development Division, GLORY Ltd., 1-3-1 Shimoteno, Himeji, Hyogo 670-8567, Japan
²Department of Computer Science and Systems Engineering, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan

(Received May 31, 2010; Revised July 30, 2010; Accepted September 10, 2010)

We propose a new method for authenticating valuable paper sheets such as gift coupons, tickets, and cheques with the use of optical coherence tomography (OCT). This method is based on the detection and evaluation of cross-sectional structural characteristics of valuable paper sheets provided with security features. Commonly used as a security feature is a security thread, which is embedded in such paper sheets. In this paper, the nondestructive detection of the embedded security thread is demonstrated using spectral-domain OCT. The results showed that the security thread was clearly visualized in the OCT image despite the highly scattering nature of papers.

Key words: optical coherence tomography, SD-OCT, valuable paper sheet, authentication, security feature, security thread, cross-sectional structural characteristic