Trade-off Maximum Average Correlation Height Research Articles

The influence of additional phase modulation of an amplitude liquid crystal STLM on the image recognition characteristics in the invariant optical digital correlator

We present the results of measurements of additional phase modulation characteristics of a serial amplitude liquid crystal spatial light modulator HoloEye LC 2002. It is found in which way the phase shift of the liquid crystal spatial light modulator depends on the applied signal. The mathematical simulation of the performance of an invariant diffractive optical-digital correlator based on a liquid crystal spatial light modulator with the amplitude-dependent phase shift is carried out using previously measured data. The correlation filters used in the work are an optimal tradeoff maximum average correlation height filter and a minimum noise and correlation energy optical correlation filter. A method for correlation filters optimization was proposed to compensate for the recognition error caused by the presence of the additional phase modulation. In some cases, the optimization allows one not only to compensate for the recognition error, but also to reduce it.

Spectral optimized asymmetric segmented phase-only correlation filter

We suggest a new type of optimized composite filter, i.e., the asymmetric segmented phase-only filter (ASPOF), for improving the effectiveness of a VanderLugt correlator (VLC) when used for face identification. Basically, it consists in merging several reference images after application of a specific spectral optimization method. After segmentation of the spectral filter plane to several areas, each area is assigned to a single winner reference according to a new optimized criterion. The point of the paper is to show that this method offers a significant performance improvement on standard composite filters for face identification. We first briefly revisit composite filters [adapted, phase-only, inverse, compromise optimal, segmented, minimum average correlation energy, optimal trade-off maximum average correlation, and amplitude-modulated phase-only (AMPOF)], which are tools of choice for face recognition based on correlation techniques, and compare their performances with those of the ASPOF. We illustrate some of the drawbacks of current filters for several binary and grayscale image identifications. Next, we describe the optimization steps and introduce the ASPOF that can overcome these technical issues to improve the quality and the reliability of the correlation-based decision. We derive performance measures, i.e., PCE values and receiver operating characteristic curves, to confirm consistency of the results. We numerically find that this filter increases the recognition rate and decreases the false alarm rate. The results show that the discrimination of the ASPOF is comparable to that of the AMPOF, but the ASPOF is more robust than the trade-off maximum average correlation height against rotation and various types of noise sources. Our method has several features that make it amenable to experimental implementation using a VLC.