Security Applications of Optical Face Recognition System: Access Control in E-Learning

The educational system has gradually shifted from a face-to-face to an e-learning system, which has become prevalent in advanced countries with the advance of information technology, and connection of global networks. Accordingly, a growing demand is emerging for more reliable individual certification with technical precision in order to measure and record learning achievements and credentials of participants. The present system has a limit in terms of registration capacity, therefore, its accuracy has often been questioned. Against this background, an individual certification system is proposed particularly for access control in e-learning. Under our proposed system, a compact optical correlator for facial recognition is employed. This correlator was previously tested for of biometrics authentication accuracy and proved highly reliable, having recorded remarkably low error rates (below 1%). The recorded error rate is sufficiently robust that the system itself can be regarded as a valid and practical viable attestation system.     

Fast Face-Recognition Optical Parallel Correlator Using High Accuracy Correlation Filter

We designed and fabricated a fully automatic fast face recognition optical parallel correlator [E. Watanabe and K. Kodate: Appl. Opt. 44 (2005) 5666] based on the VanderLugt principle. The implementation of an as-yet unattained ultra high-speed system was aided by reconfiguring the system to make it suitable for easier parallel processing, as well as by composing a higher accuracy correlation filter and high-speed ferroelectric liquid crystal-spatial light modulator (FLC-SLM). In running trial experiments using this system (dubbed FARCO), we succeeded in acquiring remarkably low error rates of 1.3% for false match rate (FMR) and 2.6% for false non-match rate (FNMR). Given the results of our experiments, the aim of this paper is to examine methods of designing correlation filters and arranging database image arrays for even faster parallel correlation, underlining the issues of calculation technique, quantization bit rate, pixel size and shift from optical axis. The correlation filter has proved its excellent performance and higher precision than classical correlation and joint transform correlator (JTC). Moreover, arrangement of multi-object reference images leads to 10-channel correlation signals, as sharply marked as those of a single channel. This experiment result demonstrates great potential for achieving the process speed of 10000 face/s.     

Compact optical duplicate system for satellite-ground laser communications: application of averaging effects

In recent years, there has been considerable interest in satellite-ground laser communication due to an increase in the quantity of data exchanged between satellites and the ground. However, improving the quality of this data communication is necessary as laser communication is vulnerable to air fluctuation. We first verify the spatial and temporal averaging effects using light beam intensity images acquired from middle-range transmission experiments between two ground positions and the superposition of these images using simulations. Based on these results, we propose a compact and lightweight optical duplicate system as a multi-beam generation device with which it is easy to apply the spatial averaging effect. Although an optical duplicate system is already used for optical correlation operations, we present optimum design solutions, design a compact optical duplicate system for satellite-ground laser communications, and demonstrate the efficacy of this system using simulations.     

Analysis of Near-Field Intensity Distributions of High-Compression Talbot Array Illuminators Using Rigorous Diffraction Theory

The technology nowadays employed in the field of binary optics allows a relatively easy fabrication of grating structures down to the wavelength region. The analysis of light propagation through such grating structures requires the use of rigorous diffraction theories such as the rigorous coupled-wave analysis (RCWA), in order to take proper account of polarization effects in the electric and magnetic field and the thickness of the grating. In this paper, we examine the near-field intensity distributions and associated illumination efficiencies of Talbot array illuminators (TAIL#x0027;s) with compression ratios of 8 and 16 using RCWA. The high illumination efficiency observed close to the grating surface is expected to bring about new applications of TAIL#x0027;s in the field of super-resolution and near-field optics.This paper was originally presented at the 2nd International Conference on Optical Design and Fabrication, ODF2000 which was held on November 15-17, 2000 at the International Conference Center, Tokyo, Waseda University, Japan.     

A Highly Accurate Face Recognition System Using Filtering Correlation

The authors previously constructed a highly accurate fast face recognition optical correlator (FARCO) [E. Watanabe and K. Kodate: Opt. Rev. 12 (2005) 460], and subsequently developed an improved, super high-speed FARCO (S-FARCO), which is able to process several hundred thousand frames per second. The principal advantage of our new system is its wide applicability to any correlation scheme. Three different configurations were proposed, each depending on correlation speed. This paper describes and evaluates a software correlation filter. The face recognition function proved highly accurate, seeing that a low-resolution facial image size (64 × 64 pixels) has been successfully implemented. An operation speed of less than 10 ms was achieved using a personal computer with a central processing unit (CPU) of 3 GHz and 2 GB memory. When we applied the software correlation filter to a high-security cellular phone face recognition system, experiments on 30 female students over a period of three months yielded low error rates: 0% false acceptance rate and 2% false rejection rate. Therefore, the filtering correlation works effectively when applied to low resolution images such as web-based images or faces captured by a monitoring camera.     

Fabrication of Near-Infrared Volume Phase Holographic Grism with High Efficiency and High Dispersion,and Its Application to a Wavelength De-multiplexing Device

We designed and developed a volume phase holographic (VPH) grism with high resolution and high efficiency in the near-infrared light domain (1550 nm) to be applied as a wavelength de-multiplexing device of a photonic network. In order to achieve both diffraction efficiency of over 80% and wavelength resolution of 0.08 nm, we newly designed and fabricated a VPH grism with high efficiency and high wavelength resolution in near-infrared wavelength region by sandwiching a VPH grating between prisms. An active feedback control technique was introduced to a two-beam interference exposure system, and we also applied it to a wavelength de-multiplexing device for a photonic network. Consequently, a VPH grism was successfully fabricated with diffraction efficiency of over 80% by employing the Bragg condition of 1550 nm at the incident wavelength from 1530 to 1570 nm, and high refractive index modulation of 0.047 was confirmed.     

Fast and Accurate Phase Retardation Measurement of 0° Twisted Nematic Liquid Crystal Panels Based on the Principle of Homodyne Receiving

We describe herein a method to measure quickly (in less than 2 min) and accurately the phase retardation between the extraordinary and ordinary axis of homogeneous or 0° twisted nematic liquid crystal panels. Owing to the homodyne detection scheme, the setup allows us to probe liquid crystal (LC) panels with an optical power down to a fraction of 1 nW and, hence makes it possible to focus the light beam to a spot of only a few wavelengths in diameter without heating or inducing observable variations in the liquid crystal. The dependence of the phase retardation on the LC driver frequency and the temperature are presented and compared with the theoretical prediction.     

Joint transform correlator for an optical face recognition system

An opto-electronic hybrid face recognition system based on real-time joint transform correlation using two types of liquid crystal spatial light modulators is proposed. The novel digital pre-processing to improve the tolerance was confirmed experimentally by face recognition from 100 references.     

Reduction of atmospheric turbulence using optical duplicate system in free-space optical communications

Optical Review - To reduce the effect of atmospheric turbulence and stabilize the optical link in free-space optical (FSO) communications, we have proposed to use an optical duplicate system (ODS)...     

All-Optical Holographic Label Processing for Photonic Packet Switching

A holographic label processor for photonic packet switching is proposed. We observe the process of time-to-space conversion for an optical code consisting of 2 ps pulses at a wavelength of 1.55 $mUm with 100 km fiber transmission. Label recognition using an angular multiplexed spectral hologram (AMSH) as a label bank is experimentally demonstrated. We also investigate the AMSH by CGH and confirm its feasibility in computer simulations.