Distortion-invariant ID tags for object identification

Abstract

Active and passive optical identification (ID) tags and readers for remote identification and verification of objects are described. We focus our attention on the design of passive ID tags to achieve distortion-invariant authentication of the information included in the optical tag. A passive ID tag will consist of an optical phase code which can be placed in a visible part of an object for remote detection. We aim to authenticate the object even if the reader captures a distorted version of the code due to in-plane rotations. Distortion-invariance is achieved by both multiplexing the information included in the ID tag and the topology of the tag. For security purposes, double-phase encryption has already been shown as an appropriate technique to encode information. By using double-phase encryption, a signature is hidden in a phase-encoded ID tag not visible by visual inspection. Once the ID tag is captured by the reader and is decrypted, a correlation-based processor verifies the decoded information with a previously stored reference signal. The proposed system may have broad applications in transportation, homeland security, and inventory control.