Pure phase correlation with improved discrimination capability

Pure phase correlation with improved discrimination capability is proposed. The improvement is achieved by designing a region of support based on the discrimination capability (DC). We propose four approaches for designing this region; some of them consider the input scene in the design, while others are input scene invariant. The performances of these approaches are compared by numerical simulation. The DC is improved significantly for the multi-object scenes even when using an input scene invariant region of support design.     

A nonlinear correlation measure for multivariable data set

The paper states that the mutual information carried by the rank sequences that are obtained from the original two sequences is a good measure of nonlinear correlation. Based on that, the nonlinear correlation information entropy (NCIE) is proposed for measuring the general relationship of a multivariable data set. NCIE uses a number in the closed interval [0, 1] to indicate the nonlinear correlation degree of the concerned multivariable data set, with 0 and 1 denotes the weakest and the strongest relationship, respectively. Data sets generated from an autoregressive model, a nonlinear chaotic Lorenz system, and a logistic function as known correlation sequences are analyzed using the proposed NCIE. The results testify the suitableness and correctness of the proposed concepts as nonlinear correlation measure.     

Input-image homogenization as a method to improve a correlator's discrimination capability

We propose an input-image preprocessing method consisting of homogenization of the image to improve the discrimination capability of a correlation-based recognition process. This method is an approximation of the optimal filter. It offers the advantage that correlation with the preprocessed images can easily be implemented in an optical correlator working with phase-only spatial light modulators.     

Modified nonlinear morphological correlation using Laplace filtering

A Laplace filtering based morphological correlation (LBMC) is proposed as a modified approach to improve the properties of the classical morphological correlation (MC). For the LBMC, power spectrum of Laplace operator is introduced to filter the joint power spectrum (JPS) of the MC before final inverse Fourier transform. Computer simulation results show that, as compared with the linear correlation (LC) and the conventional MC, LBMC provides better discrimination capability with sharp and unmistakable correlation signal and its performance metrics are more stable when input scene is corrupted by outlier noise (salt-and-pepper noise) and additive white Gaussian noise. Although the LBMC is not illumination invariant when multiplication illumination factor is larger than unity, considerable discrimination capability is still obtained.     

Feedback controlled periodic states for different kinds of photorefractive nonlinear response

We investigate analytically and numerically the influence of the type of the photorefractive nonlinear response on the periodic states (attractors) which occur during feedback controlled 2W-coupling and correspond to almost 100% diffraction efficiency of the dynamic index grating. In addition to the case of the local response typical, for example, for LiNbO₃ crystals we consider the cases of nonlocal (diffusive) response (BaTiO₃, SBN) and resonant response (DC-biased BSO, BTO, and BGO crystals). It is shown that the conditions for the transition to the periodic states and their apparent characteristics are strongly different for the two limiting cases above. Received 16 July 2002 / Received in final form 29 October 2002 Published online 4 March 2003     

Interaural correlation discrimination: II. Relation to binaural unmasking

Many theoretical models of binaural interaction assume that sensitivity to interaural correlation underlies binaural unmasking. This paper explores the extent to which sensitivity to changes in interaural correlation implied by results from binaural detection experiments are consistent with sensitivity to changes in interaural correlation implied by results from binaural detection experiments are consistent with sensitivity to changes in interaural correlation measured directly in correlation discrimination experiments. The vehicle for this exploration is a simplified model of the underlying processes assumed by many models of binaural unmasking for the detection of narrow-band signals in the presence of broadband noise. Consideration is given to psychometric function slopes, detection thresholds, bandwidth effects, duration effects, level effects, and interaural-parameter effects. Although many of the results obtained from our analysis are consistent with the notion that the cue in binaural detection tasks is a change in interaural correlation, some significant inconsistencies are noted.     

Weighted least-squares phase unwrapping algorithm based on derivative variance correlation map

Among different phase unwrapping approaches, the weighted least-squares minimization methods are gaining attention. In these algorithms, weighting coefficient is generated from a quality map. The intrinsic drawbacks of existing quality maps constrain the application of these algorithms. They often fail to handle wrapped phase data contains error sources, such as phase discontinuities, noise and undersampling. In order to deal with those intractable wrapped phase data, a new weighted least-squares phase unwrapping algorithm based on derivative variance correlation map is proposed. In the algorithm, derivative variance correlation map, a novel quality map, can truly reflect wrapped phase quality, ensuring a more reliable unwrapped result. The definition of the derivative variance correlation map and the principle of the proposed algorithm are present in detail. The performance of the new algorithm has been tested by use of a simulated spherical surface wrapped data and an experimental interferometric synthetic aperture radar (IFSAR) wrapped data. Computer simulation and experimental results have verified that the proposed algorithm can work effectively even when a wrapped phase map contains intractable error sources.     

Three-field noise correlation via third-order nonlinear optical processes

We report experimental observation of three-field noise correlation between two coexisting four-wave mixing (FWM) signals and the probe signal in a coherently-prepared rubidium vapor system. The two FWM signals in a double-Λ type quasi-four-level atomic system are obtained in different directions via their respective phase-matching conditions and can be detected individually. These signals and the probe beam are found to be strongly correlated or anticorrelated with each other.     

Interference analogy of Raman-luminescence problem and experimental discrimination by polarization correlation

Light scattering and luminescence under resonant optical excitation are shown to correspond to an interference fringe and broad background, respectively, in an optical interference experiment, if suitable definitions for the above two processes are adopted. It is proposed to discriminate between these two by a polarization measurement which is analogous to an interference experiment. The results of such an experiment in ZnSe and ZnTe are also reported.     

Structure of the correlation dependence of nonlinear stochastic functionals

Radiophysics and Quantum Electronics -     

Weighted Information and Weighted Entropic Inequalities for Qutrit States

We review the notion of weighted quantum entropy and consider the weighted quantum entropy for bipartite and noncomposite quantum systems. We extend the subadditivity condition, the inequality known for the weighted entropy information, to the case of indivisible qudit system, such as a qutrit. We discuss the new inequality for the qutrit density matrix for different weights and states, as well as the role of weighted entropy with respect to nonlinear quantum channels.     

A spatial correlation method for reconstructing blood flow velocity vector in the nonlinear tomography

A method for reconstructing the total blood flow velocity vector distribution is proposed. Experimental data are obtained with the help of the second-order nonlinearity parameter tomography scheme that employs wideband coded signals and a small number of transducers. The data are processed using the selective matched filtering technique in combination with spatial correlation of fragments of the speckle structure that appears in the process of reconstruction of the spatial nonlinearity parameter distribution. Results of numerical simulations are presented.     

A nonlinear correlation method using multiphoton ionization for the measurement of uv ultrashort pulses

A new nonlinear correlation method which makes it possible to measure the duration of uv ultrashort pulses has been proposed. In this method the multiphoton ionization of gases is used as a nonlinear process and the ion current caused by the process is detected. We have also experimentally demonstrated its usefulness in the uv region by observing the second- and the third-order auto-correlation profiles of picosecond pulses at 2661 Å (the fourth harmonic of a mode-locked YAG laser), using NO and Xe gases, respectively.     

Sliced orthogonal nonlinear generalized decomposition based fringe-adjusted joint transform correlation

A sliced orthogonal nonlinear generalized (SONG) decomposition based version of modified fringe-adjusted joint transform correlator (MFJTC), SBFJTC, is proposed. In SBFJTC scheme, the reference and input scenes are decomposed into a set of binary slices through SONG decomposition. MFJTC filtering of each pair of binary slices, corresponding to the same gray level of reference and input scene, is performed and then the outputs are added. Numerical simulations show that the proposed scheme delivers a better correlation performance and robustness to the white additive Gaussian noise, substitutive noise and nonoverlapping noise than that of both of the FJTC and the MFJTC.     

Optical authentication via photon-synthesized ghost imaging using optical nonlinear correlation

We present a method for optical authentication via photon-synthesized ghost imaging using optical nonlinear correlation. In ghost imaging, multiple series of photons recorded at the object beam arm can be arbitrarily controlled for the generation of synthesized objects. Ghost imaging with sparse reference intensity patterns provides a channel to effectively modulate the noise-like synthesized objects during the recovery, and the reconstructed (noise-like) objects, i.e., added or subtracted information, can be further authenticated by optical nonlinear correlation algorithm. It is expected that the proposed method can provide an effective and promising alternative for ghost-imaging-based optical processing.     

Coloured noise controlled dynamics of nonlinear polaritons in semiconductor microcavity

The coloured noise induced escape rate from the lower energy stable state of a driven nonlinear microcavity oscillator has been investigated by means of quasi-classical kinetic equations. We show that for coloured, i.e. narrow-band, relatively intense noise, the escape time is controlled by the interplay of two mechanisms: the noise induced drift and adiabatic regular shift of the oscillator state towards unstable saddle point. The cross-over between these mechanisms takes place in a particular range of the driving field intensity values, depending on the ratio between the oscillator damping and the coloured noise spectrum width. The dependence of the transition rate on the noise correlation time is analyzed for wide range of correlation time values. The article is published in the original.