Compact Parallel Optical Correlator for Face Recognition, and Its Application

With the ongoing progress in information technology, the need for an accurate personal identification system based on recognizing biological characteristics is increasing demand for this type of security technology, rather than conventional systems that use ID cards or pin numbers. Of all physical features, the face is the most familiar and recognizable, and using it for identification purposes avoids the need for physical contact, thereby also avoiding potential psychological or physical resistance, such as that encountered when trying to obtain fingerprints for example. Face recognition has been studied since the 1970s, with extensive research into and development of the digital processing of facial images. A range of software is already on the market. As a simple and compact recognition system that satisfies the required performance levels, we have implemented a hybrid system based on the optical recognition principle, using a Fourier transform lens. In contrast to digital recognition, optical analog operations process two-dimensional images instantaneously in parallel using a lens-based Fourier transform function (Kodate Hashimoto, & Thapliya, 1999). In the 1960s, two methods were proposed; the VanderLugt Correlator proposed by VanderLugt ((a)Watanabe & Kodate, 2005), and the joint transform correlator (JTC) ( Kodate Inaba & Watanabe, 2002) by Weaver and Goodman. The optical correlator by the Institut national d’Optique in Canada gained the New Product Award at the 1999 Conference on lasers and Electro-optics and the Quantum Electronics and Laser Science Conference. In Japan the conventional JTC was practically implemented by the Hamamatsu Photonics Company for fingerprint image processing. The process speed of optical correlators has steadily improved, however, operational speed, practicality and recognition rate were not fully tested against the fast-improving digitized system. Against this background, the present group of authors has proposed a new scheme using a multi-beam, multi-channel parallel joint transform correlator (PJTC) as a means of making better use of spatial parallelism through the use of a diffraction-type multi-level zone-plate array (MLZP array) to extend a single channel JTC ((b)Watanabe & Kodate , 2005). Watanabe & Kodate , 2003). Features of the proposed system include extreme robustness, high recognition precision by its pre-processing and high reproducibility by its post-process. The compact and mobile versions are now assembled and named COPaC. Specifications: 20x24x43 cm 3.6 kg, analysis time of 6.6 faces/s ( Kodate Inaba& Watanabe, 2002).