Infrared Small Target Detection Based on Multiscale Kurtosis Map Fusion and Optical Flow Method.

The uncertainty of target sizes and the complexity of backgrounds are the main reasons for the poor detection performance of small infrared targets. Focusing on this issue, this paper presents a robust and accurate algorithm that combines multiscale kurtosis map fusion and the optical flow method for the detection of small infrared targets in complex natural scenes. The paper has made three main contributions: First, it proposes a structure for infrared small target detection technology based on multiscale kurtosis maps and optical flow fields, which can well represent the shape, size and motion information of the target and is advantageous to the enhancement of the target and the suppression of the background. Second, a strategy of multi-scale kurtosis map fusion is presented to match the shape and the size of the small target, which can effectively enhance small targets with different sizes as well as suppress the highlighted noise points and the residual background edges. During the fusion process, a novel weighting mechanism is proposed to fuse different scale kurtosis maps, by means of which the scale that matches the true target is effectively enhanced. Third, an improved optical flow method is utilized to further suppress the nontarget residual clutter that cannot be completely removed by multiscale kurtosis map fusion. By means of the scale confidence parameter obtained during the multiscale kurtosis map fusion step, the optical flow method can select the optimal neighborhood that matches best to the target size and shape, which can effectively improve the integrity of the detection target and the ability to suppress residual clutter. As a result, the proposed method achieves a superior performance. Experimental results on eleven typical complex infrared natural scenes show that, compared with seven state-of-the-art methods, the presented method outperforms in terms of subjective visual effect, as well as some main objective evaluation indicators such as BSF, SCRG and ROC, etc.

Wavelet-Based Contourlet Transform and Kurtosis Map for Infrared Small Target Detection in Complex Background.

Wavelet-based Contourlet transform (WBCT) is a typical Multi-scale Geometric Analysis (MGA) method, it is a powerful technique to suppress background and enhance the edge of target. However, in the small target detection with the complex background, WBCT always lead to a high false alarm rate. In this paper, we present an efficient and robust method which utilizes WBCT method in conjunction with kurtosis model for the infrared small target detection in complex background. We mainly made two contributions. The first, WBCT method is introduced as a preprocessing step, and meanwhile we present an adaptive threshold selection strategy for the selection of WBCT coefficients of different scales and different directions, as a result, the most background clutters are suppressed in this stage. The second, a kurtosis saliency map is obtained by using a local kurtosis operator. In the kurtosis saliency map, a slide window and its corresponding mean and variance is defined to locate the area where target exists, and subsequently an adaptive threshold segment mechanism is utilized to pick out the small target from the selected area. Extensive experimental results demonstrate that, compared with the contrast methods, the proposed method can achieve satisfactory performance, and it is superior in detection rate, false alarm rate and ROC curve especially in complex background.

Focusing phenomenon based on the coupling effect of acoustic waveguide.

We investigated the coupling effect in a pair of parallel acoustic cladded waveguides and extended the effect to obtain energy focusing in a specially structured waveguide of nested pipes. For the structure composed of two parallel waveguides, we simulated and verified that when an acoustic input wave propagates in one waveguide, the wave couples with the other and alternates between the two parallel waveguides with periodic amplitude and a well-defined coupling length. This length is related to the frequency of the input wave and the structure of the waveguide. Moreover, we fabricated a specially structured waveguide composed of four concentric circular pipes. In both simulations and experiments, we further demonstrated that the acoustic wave transmitted through designated ports of this fabricated waveguide structure can be focused onto the central waveguide with a well-defined focusing length, and that the focusing length is related to the wave frequency. Similar to its optics counterpart, not only can the coupling effect between the acoustic cladded waveguides be used in energy focusing in the nested waveguide structure, but it can also be used in other acoustic wave controlling devices, such as the frequency-selective device, the power switch for an acoustic wave, and the highly efficient pure-mode transducer.

Fluorescent Binary Ensemble Based on Pyrene Derivative and Sodium Dodecyl Sulfate Assemblies as a Chemical Tongue for Discriminating Metal Ions and Brand Water.

Enormous effort has been put to the detection and recognition of various heavy metal ions due to their involvement in serious environmental pollution and many major diseases. The present work has developed a single fluorescent sensor ensemble that can distinguish and identify a variety of heavy metal ions. A pyrene-based fluorophore (PB) containing a metal ion receptor group was specially designed and synthesized. Anionic surfactant sodium dodecyl sulfate (SDS) assemblies can effectively adjust its fluorescence behavior. The selected binary ensemble based on PB/SDS assemblies can exhibit multiple emission bands and provide wavelength-based cross-reactive responses to a series of metal ions to realize pattern recognition ability. The combination of surfactant assembly modulation and the receptor for metal ions empowers the present sensor ensemble with strong discrimination power, which could well differentiate 13 metal ions, including Cu2+, Co2+, Ni2+, Cr3+, Hg2+, Fe3+, Zn2+, Cd2+, Al3+, Pb2+, Ca2+, Mg2+, and Ba2+. Moreover, this single sensing ensemble could be further applied for identifying different brands of drinking water.

Discrimination of Metalloproteins by a Mini Sensor Array Based on Bispyrene Fluorophore/Surfactant Aggregate Ensembles.

Fluorescent sensor arrays with pattern recognition ability have been widely used to detect and identify multiple chemically similar analytes. In the present work, two particular bispyrene fluorophores containing hydrophilic oligo(oxyethylene) spacer, 6 and 4, were synthesized, but one is with and the other is without cholesterol unit. Their ensembles with cationic surfactant (CTAB) assemblies realize multiple fluorescence responses to different metalloproteins, including hemoglobin, myoglobin, ferritin, cytochrome c, and alcohol dehydrogenase. The combination of fluorescence variation at monomer and excimer emission of the two binary sensor ensembles enables the mini sensor array to provide a specific fingerprint pattern to each metalloprotein. Linear discriminant analysis shows that the two-ensemble-sensor-based array could well discriminate the five tested metalloproteins. The present work realizes using a mini sensor array to accomplish discrimination of complex analytes like proteins. They also display a very high sensitivity to the tested metalloproteins with detection limits in the range of picomolar concentration.

A center frequency adjustable narrow band filter for the detection of weak single frequency signal.

We describe and implement a center frequency adjustable narrow band filter based on the crystal filter for the detection of weak single frequency signal. It is formed by a multiplier, a direct digital frequency synthesizer, a multi-stage crystal bandpass filter, and a micro control unit which is used to set the center frequency of the filter. A theoretical study is proposed and experimentally validated. The test results show that the 3 db and 20 db bandwidths are 0.84 Hz and 2.73 Hz, respectively, and the filter system can effectively detect the signal with amplitude below 1 µV and a frequency which ranges from 10 Hz to the frequency that is mainly limited by the components applied.

A portable and autonomous multichannel fluorescence detector for on-line and in situ explosive detection in aqueous phase.

A multichannel fluorescence detector used to detect nitroaromatic explosives in aqueous phase has been developed, which is composed of a five-channel sample-sensor unit, a measurement and control unit, a microcontroller, and a communication unit. The characteristics of the detector as developed are mainly embedded in the sensor unit, and each sensor consists of a fluorescent sensing film, a light emitting diode (LED), a multi-pixel photon counter (MPPC), and an optical module with special bandpass optical filters. Due to the high sensitivity of the sensing film, the small size and low cost of LED and MPPC, the developed detector not only has a better detecting performance and small size, but also has a very low cost - it is an alternative to the device made with an expensive high power lamp and photomultiplier tube. The wavelengths of the five sensors covered extend from the upper UV through the visible spectrum, 370-640 nm, and thereby it possesses the potential to detect a variety of explosives and other hazardous materials in aqueous phase. An additional function of the detector is its ability to function via a wireless network, by which the data recorded by the detector can be sent to the host computer, and at the same time the instructions can be sent to the detector from the host computer. By means of the powerful computing ability of the host computer, and utilizing the classical principal component analysis (PCA) algorithm, effective classification of the analytes is achieved. Furthermore, the detector has been tested and evaluated using NB, PA, TNT and DNT as the analytes, and toluene, benzene, methanol and ethanol as interferent compounds (concentration various from 10 and 60 µM). It has been shown that the detector can detect the four nitroaromatics with high sensitivity and selectivity.

A portable fluorescence detector for fast ultra trace detection of explosive vapors.

This paper developed a portable detector based on a specific material-based fluorescent sensing film for an ultra trace detection of explosives, such as 2,4,6-trinitrotoluene (TNT) or its derivate 2,4-dinitrotoluene (DNT), in ambient air or on objects tainted by explosives. The fluorescent sensing films are based on single-layer chemistry and the signal amplification effect of conjugated polymers, which exhibited higher sensitivity and shorter response time to TNT or DNT at their vapor pressures. Due to application of the light emitting diode and the solid state photomultiplier and the cross-correlation-based circuit design technology, the device has the advantages of low-power, low-cost, small size, and an improved signal to noise ratio. The results of the experiments showed that the detector can real-time detect and identify of explosive vapors at extremely low levels; it is suitable for the identification of suspect luggage, forensic analyses, or battlefields clearing.