Experimental demonstration of the hybrid opto-electronic correlator for target recognition

Abstract

Optical target recognition using correlators is an important technique for fast verification and identification of images. The hybrid opto-electronic correlator (HOC) recently proposed by us bypasses the need for nonlinear materials such as photorefractive polymer films by using detectors instead, and the phase information is yet conserved by the interference of plane waves with the images. In this paper, we demonstrate experimentally the basic working principle of the HOC architecture using currently available technologies. For matched reference and query images, the output signal shows a sharp peak, indicating a match is found. For an unmatched case, a much lower peak value is observed, indicating no match. We also demonstrate the dependence of the output signal on the phases of the interfering plane waves and describe a technique using an interferometer and a servo for optimizing the output signal. As such, the work reported here paves the way for further development of the HOC for practical applications.

Optical Correlators for Cryptosystems and Image Recognition: A Review

“…To further improve the operational speed of the correlator, the same group [ 121 , 122 ] proposed the use, as optical storage database of high capacity, a holographic memory device (HMD) based on the polymer substrate PQ:PMMA (Phenanthrenequinone-doped poly(methyl methacrylate)), and experimentally validated the feasibility and efficiency of introducing, in the HOC correlator, the PQ:PMMA HMD. Monjur et al [ 8 ] validated, by means of experiments, the functioning principle of a HOC correlator previously proposed by the same group. Sharp and lower correlation peaks, respectively, were observed in the matched and unmatched cases when the input and reference images were compared, with a 14 times higher amplitude of the peaks in the output signal for the matched case.…”

“…As opposed to holographic correlators and to the classical JTC and VLC setups, the hybrid opto-electronic correlator (HOC) benefits from better materials employed for recording: films of photorefractive polymers are replaced by materials with photodetection properties [ 8 ]. Moreover, as compared to the VLC correlator where the comparison of two images can be achieved by employing a holographic filter, the HOC correlator increases the speed by eliminating the slow process of recording required by the filters.…”

“…The photodetectors are used for recording the data about the amplitude and phase of both target and reference images, by means of the interference with planar waves. The reliability of this type of correlator was recently demonstrated experimentally [ 8 ]. Another type of correlator that is not all-optical is the electro-optic correlator used for microwave interferometry.…”

“…The speed is envisioned to be further improved, up to an ideal value of approximately 5 μs per correlation, using optoelectronic integrated circuits, customized for this type of correlator [ 121 ]. Another enhancement for the HOC correlator, proposed by Monjur et al [ 8 ], was to include a new component, not yet developed, named the IGPU (Integrated Graphic Processing Unit) that enables an increase of the speed such that a correlation operation could be performed in only several microseconds, by avoiding the considerable slowing down due to serial communications between SLMs, FPGAs (field programmable gate arrays), cameras and other components of the correlator setup.…”

“…The first one involves the design of novel correlation filters to improve the methods of correlation, whereas the second deals with biometric applications, in turn with several main directions: face recognition (the most frequent one, with early and recent applications in building access control [ 5 ], video surveillance, unmanned vehicles, identification of law breakers etc. [ 1 ]), recognition of moving targets (e.g., boats, aircrafts, missiles) in a complex background, detection of fingerprints, robotics, military (defense) uses, medical applications for an automatic early detection of various diseases, by detection and matching of various biological samples [ 1 , 6 , 7 , 8 , 9 , 10 ].…”