Spectrum detection and analysis
2018, 47(8): 823001.
doi: 10.3788/IRLA201847.0823001
An green algae area estimation algorithm for hyperspectral image based on linear mixed model was proposed. According to the obtained endmembers and the original image, the abundance map of the green algae terminal was calculated by the fully constrained least squares algorithm, and the abundance map of green algae was regarded as the area estimation result directly. The algorithm can effectively overcome the problem of inaccurate estimation of the estimated area of green algae due to the lack of resolution of hyperspectral image, and realize the estimation of green algae area at sub-pixel level. Based on the Geostationary Ocean Color Imager (GOCI) 8 bands image unfolding experiment on June 29, 2013, the estimated coverage of green algae was 321 km2, which was close to that of HJ-1B satellite. Compared with NDVI and other traditional algorithms, the proposed method has obvious advantages. Traditional methods usually present higher estimation results, because they could only justify whether a pixel includes green algae or not. The proposed method may provide a new way of thinking and technology for early warning and monitoring of green algae, and has a high application value.
2018, 47(8): 823002.
doi: 10.3788/IRLA201847.0823002
In order to test and analyze the physical evidence of plastic beverage bottles, 57 samples of plastic beverage bottles were inspected by Fourier transform infrared spectrometer(FTIR), X-ray fluorescence spectrometer (XRF) and thickness meter, and analyzed and treated by means of cluster analysis. Firstly, the main components of plastic beverage bottles were tested by infrared spectroscopy. According to the different components of the samples, they can be divided into polyethylene (PE) and polyethylene terephthalate (PET). Secondly, the main filler calcium carbonate in the sample can be determined by X-ray fluorescence spectrometry, and the samples can be distinguished according to the content of Ca elements. Finally, the thickness of plastic beverage bottle sample can be measured by thickness meter. According to the color, specification, composition, Ca content and sample thickness of the samples, the samples can be distinguished by the cluster analysis method. The experimental results show that the method is simple, fast, accurate, reliable and non-destructive, and can be used to distinguish and inspect plastic beverage bottles.
2018, 47(5): 523001.
doi: 10.3788/IRLA201847.0523001
In order to inspect accurately the condition of early wheat powdery mildew, and also to provide technical support for spraying pesticides, in this study hyperspectral imagery data of different disease severity for wheat leaves were collected at the early infection stage. Firstly, the leaf area and lesion area were segmented by image features, and then the disease severity was calculated quantitatively. Secondly, the Relief-F algorithm was introduced to select the most sensitive band and band difference, on the basis, the powdery mildew disease index(PMDI) was calculated. Moreover, the correlations between disease index(DI) and 11 vegetation indices(Including PMDI index) were analyzed, it was found that the PMDI index has the highest coefficient of determination(R2=0.839 9) and the lowest root-mean-square error(RMSE) which is 4.522 0. It was better than that of other disease vegetation indices, in which the result of normalized difference vegetation index(NDVI) was the highest, the determination coefficient is 0.777 1 and the RMSE equals 5.336 4. Finally, the support vector regression(SVR) models of PMDI and NDVI indexes were established, respectively, to further compare the retrieval performance for disease severity of early wheat powdery mildew. The result shows that the prediction model of PMDI index is better than NDVI index, the R2 is 0.886 3 with RMSE=3.553 2. It can be concluded that the developed method can effectively realize nondestructive diagnosis of early wheat powdery mildew, and provide important help for the spraying and disease control.
2018, 47(12): 1223001.
doi: 10.3788/IRLA201847.1223001
The algorithm was proposed based on the empirical mode decomposition and regression analysis to extract and identify the characteristic information of spatial heterodyne spectroscopy. The spectrum which was obtained by pre-processing the original probe data was decomposed into several intrinsic mode function components by empirical mode decomposition and the each order IMF's Pearson correlation coefficient was calculated with the original spectral signal. According to the correlation coefficient classification criteria, the demarcation point of the background and target information reconstruction will be determined. Then the Pearson correlation coefficient between the reconstructed background and the measured background was calculated to determine the empirical mode decomposition results. At the same time, the signal-dominated components were de-noised respectively by the wavelet soft threshold and then the pure target characteristic signal was reconstructed. By using multiple linear regression analysis to process the target characteristic information and the original interference spectral information, the optimal coefficients of time-domain filtering will be obtained. The filter will be constructed to extract the target. Finally, the signal of extracted target will be identified by Pearson correlation coefficients. The experimental results show that the background and the target can be separated by the empirical mode decomposition. In the case of unknown background signal, the empirical mode decomposition and regression analysis can be used to extract the characteristic spectrum of potassium resonance.
2018, 47(1): 123001.
doi: 10.3788/IRLA201847.0123001
In order to solve the problem of complex and time-consumption of reference signal zero crossings in the traditional Brault sampling method, a method based on Fourier interpolation technique was proposed to find the zero-crossing. Compared with other interpolation methods, the results showed that this method could ensure the accuracy of zero-crossing information and simplify the complexity of data processing. The linear fitting coefficient of zero-crossing information obtained was greater than 0.999. In the range of 2 100-2 200 cm-1, when the error of reference laser signal was small, the instrumental SNR obtained by the Fourier interpolation method was 1.03 times that obtained by the cubic spline interpolation method, and the result obtained by the linear interpolation method was consistent with Fourier interpolation method. When the error of reference laser signal was relatively large, the instrumental SNR obtained by the Fourier interpolation method was 1.05 times of the SNR obtained by the linear interpolation method.
2018, 47(1): 123002.
doi: 10.3788/IRLA201847.0123002
The accuracy of polarized detection for field-portable spectropolarimeter directly influences the precision of polarization spectrum of ground object, and thus affects the interpretation accuracy of the polarized characteristic of targets. A polarization measurement group unit was designed for grating spectrometer. Then the two kinds of grating spectrometers were transformed into spectropolarimeters. Based on variable polarization light source, the performances of the two spectropolarimeters were verified. The polarization sensitivity of the two spectropolarimeters was analyzed at first. The different degree of polarization spectra output from variable polarization light source was measured using the two spectropolarimeters. The results show that both of them have polarization sensitivity and the degree of polarization of output light measured by the two spectropolarimeters are consistent with the theoretical output of the variable polarization light source. The error between theoretical output and measured results are within 2% when the wavelength range is from 460 nm to 920 nm. It verifies that the feasibility of two spectropolarimeter polarization measurement group unit which could meet the experiment requirements.
2017, 46(4): 423001.
doi: 10.3788/IRLA201746.0423001
Interferograms in the photo-elastic modulator Fourier transform spectrometers(PEM-FTS)has high modulation frequency, and its modulated optical path difference is continuous nonlinear. In order to improve the accuracy and stability of the rebuilt spectrums whose interferograms is sampled by the equal time intervals, it is necessary to study the technology of pretreatment and phase correction of photo-elastic modulated interferograms. In the paper, the characteristic that the amplitude of the zero optical path difference was maximum in a interferogram were used to derive these data of a interferogram. Simultaneously, the method which combined the improved Mertz method and the accelerated nonuniform fast Fourier transform algorithm (NUFFT) was put forward to resolve the asymmetric and to improve the velocity and precision of the rebuilt spectrum. In the experiment, the asymmetrical photo-elastic modulated interferograms of 300 K infared blackbody were generated by simulation, the data processing algorithm was applied to enhance the accuracy of the rebuild spectrum, and the atmosphere spectral curve was rebuilt and gas components were qualitative analyzed with the atmosphere window as the measured object.
2017, 46(3): 323001.
doi: 10.3788/IRLA201746.0323001
Underwater multispectral imaging is a promising technique for high-fidelity underwater color reproduction and mapping of kelp, sea grass, corals, etc. However, as light propagates through water, light is severely absorbed and scattered by water, causing image dim, hazy and distorted in its spectrum and color. In this paper, calibration of water attenuation coefficient based on underwater images and restoration of underwater multispectral images are discussed. Multispectral images of an underwater object are captured at different underwater distances. Technique has been proposed to calibrate the water attenuation coefficient based on underwater images of different distances and restore the raw images. Analysis was also conducted to search for the least number of distances for coefficient calibration and restoration. By comparing the restored underwater images with the images captured in air, its found that the technique proposed in this paper provides accurate restoration of underwater spectral images, with a relative residual error of 5.87% in average for all test images.
2017, 46(2): 223001.
doi: 10.3788/IRLA201746.0223001
For the purpose of enhancing the stability and enlarging the dynamic range in trace gas sensing, the conventional wavelength modulation spectroscopy technology was improved by the introduction of logarithmic-transformed data processing method and differential detection circuit. Before the extraction of the gas absorption related harmonics using a lock-in amplifier, the logarithmic-transformation and the differential detection were fulfilled by a homemade receiver. Through the logarithmic-transformation, the optical intensity modulation of the laser emitting was separated from the absorption-induced power attenuation, and then the former was balanced during differential detection. Owing to this two-pronged strategy, each harmonic component of the absorption spectrum can be theoretically captured without the interferences of residual amplitude modulation and harmonic distortion. For the validation of theory, the second harmonic of P(6) absorption line for NH3 was acquired. The experimental temperature and total pressure were maintained at 296 K and 1.01105 Pa, respectively. Under the effective path length of 24.5 cm, a 0.7 ppm (part per million) detection limit was deduced on the assumption that the amplitude of signal was weakened to be equal with the noise. The above results indicate that this scheme is an ideal option for trace gas detection application.
2017, 46(11): 1123001.
doi: 10.3788/IRLA201746.1123001
Shenmai injection is compound traditional medicine and widely employed in adjuvant therapy of cancer patients for improving the patient's life. The interaction of Shenmai injection with human serum albumin(HSA) in physiological buffer(PH 7.4) was investigated by fluorescence spectroscopy and UV-Vis absorption spectroscopy. These results have significant importance for understanding the pharmacological action pesticide effect of Shenmai injection. Shenmai injection can effectively quench the intrinsic fluorescence of HSA and the results shown that the quenching mechanism was a dynamic process, which was further proved by the UV-Vis absorption spectroscopy. The binding constant KA at different temperatures(296, 303, 310 K) were obtained from Modified Stern-Volmer analysis of the fluorescence quenching data. The thermodynamic parameters were calculated by Van't Hoff equation(△G0, △H0, △S0). It indicated that the hydrophobic interactions play an important role in the interaction of Shenmai injection and HSA. In addition, the binding process was spontaneous. Furthermore, the synchronous fluorescence spectra showed that the maximum fluorescence peak of tyrosine residues changed which meant the binding of Shenmai injection to HSA mainly acting on tyrosine residues and the interaction can induce the microenvironment and conformation changes of HSA.
2017, 46(11): 1123002.
doi: 10.3788/IRLA201746.1123002
Raman spectroscopy has been more and more frequently used for pesticide residue detection research in recent years, but the development of sample pretreatment technology is relatively lagging behind. In the study, a rapid method had been developed for the determination of imidacloprid residue in cucumbers with the application of Raman spectroscopy technology and Quick Easy Cheap Effective Rugged and Safe(QuEChERS) sample preparation. Three batches of cucumber samples (the concentration of imidacloprid was within the range of 0.2-5 mg/kg) with different preparation steps(acetonitrile extraction, dehydrate extraction, and fading removing impurity) were chosen as experimental objects. Confocal micro Raman spectrometer was utilized with a 780 nm laser to collect three batches of samples of Raman spectra. Six quantitative prediction models of imidacloprid residue were established based on PLS and PCR methods. The results showed that in addition to the PCR model of the samples by two steps preparation, the residual predictive deviation(RPD) of the other five models was higher than 3. The samples which were only extracted with acetonitrile got the best modeling effect. The correlation coefficient of the calibration set and the prediction set were all above 0.99. The root mean square error of prediction(RMSEP) of PLS method was 0.148 mg/kg, and the RPD was 5.52, which obtained the highest precision of the six predictive models. The results could provide a strong basis for the following-up studies.
2017, 46(10): 1023001.
doi: 10.3788/IRLA201790.1023001
The non-linearity caused by the detector of the Fourier transform spectrometer was studied, and the influence of non-linearity on the spectrum was discussed. The quadratic non-linearity correction methods were also discussed:convolution method and iterative method. Then the two methods were used to correct the nonlinear data. A new method which is more suitable for practical data was proposed based on both convolution method and iterative method. Finally, the three methods were used to correct the non-linearity of the simulated data and the actual data. The experimental data shows that the nonlinear performance of the data after correction was restrained. And it was found that compared with the other two methods, the new method has better accuracy and faster speed.
2017, 46(10): 1023002.
doi: 10.3788/IRLA201791.1023002
A convenient and rapid, sensitive and accurate, and non-destructive method was established to analyze rubber sole. It provides clues, indicates investigation direction for the detection, and provides the scientific basis for proving the crime. Rubber sole samples was tested by using X-ray energy dispersive spectroscopy (EDS) to provide scientific basis for verifying crime. The test parameters were set as the following:voltage was 45 kV, test current was 40 A, power was 1.8 kW, the size of sample was 1.5 cm1.5 cm, and testing time was set as 60 s. The qualitative and semi-quantitative analysis of inorganic elements in 40 different rubber sole samples of different brands and different types was carried out, and the reproducibility of the method was examined. At the same time, the rubber sole samples were classified using SPSS clustering analysis-center of gravity method as definition of distance between the classes. Consequently, the method has the characteristics of accurate and reliable result, good reproducibility, no need for sample preparation and non-destructive testing. It can be used for public security organs to resolve the cases.
2016, 45(S2): 120-125.
doi: 10.3788/IRLA201645.S223001
A novel non-negative sparse representation (NSR) model was proposed for hyperspectral anomaly detection. The key idea was that a background pixel can be approximately represented as a sparse linear combination of its surrounding neighbors, while an anomalous pixel cannot. The non-negativity and one-to-one constraints on the sparse vector were imposed for physical meaning and better discrimination power of the algorithm. In order to exclude the potential anomalous pixels presented in the background dictionary, the atoms which were similar to the center pixel was pruned. Then the NSR model was solved by non-negative orthogonal matching pursuit (NOMP) algorithm, and the reconstruction errors were directly used for determining the anomalies. Finally, experimental results on real hyperspectral data set demonstrate the effectiveness of the proposed algorithms by comparing it with state-of-the-art algorithms.
2016, 45(S2): 126-131.
doi: 10.3788/IRLA201645.S223002
The traditional registration method is based on the search area registration and it is carried out at control points of the image coordinates of discrete points, but this method will limit the positioning accuracy of the registration control point. Aiming at this problem, a high spectral registration method which is based on Gaussian fitting was preseuted. Similar to the traditional registration method based on region, this method also used the gray information of images to build the similarity measure between two images and searched the point at which the similarity measure can reach its maximum or minimum to be the registration control points. Different with the traditional methods, it did not go straight for the extreme point and used it as the registration control point during the process of search, instead, the similarity-matrix was produced at first during the process of search and coefficients of Gaussian fitting function could be obtained from the value near the extreme points, the extreme points of Gaussian fitting function were used as the registration control points to complete the registration. The multiple sets of experimental results of hyperion high spectral registration all show that the method presented in the paper is more accurate than the traditional methods, and the registration accuracy reaches sub-pixel successfully, the method can meet the follow-up demands such as fusion, change detection and so on.
2016, 45(S2): 132-139.
doi: 10.3788/IRLA201645.S223003
To solve the problem that traditional hyperspectral target detection is based on either airborne image or spaceborne image, and doesn't utilize the advantage of aerial and space imaging comprehensively, a target detection method for airborne and spaceborne image fusion, which combined 3D GMRF with D-S evidence theory, was proposed in this paper. The 3D GMRF detection results from airborne image and spaceborne image were fused by D-S evidence theory in decision level. The experimental results show that the proposed target detection method complements the advantage of aerial hyperspectral image and space hyperspectral image, and enhances accuracy on target detection. This technology is new target detection method by fusing the aerial and space hyperspectral image.
2016, 45(S1): 121-126.
doi: 10.3788/IRLA201645.S123001
The core of the satellite characteristics inversion based on mixed satellite spectra is the mathematical model and inversion algorithm. Theoretical model of spectral mixing was built with experiments conducted to justify the model. First, theoretical analysis of components' spectral scattering model, linear spectral mixing model and unmixing methods of satellite's spectral data was conducted. Then, experiments were designed to measure and calibrate the spectral BRDF of a high-fidelity GEO satellite and its components, while the spectral scattering characteristics of component and material were discussed. Finally, nonnegative constrained least square methods were utilized to unmix the satellite's spectral data, with the largest relative residue less than 10%. Experiment results show that the linear spectral mixing model and nonnegative constrained least square unmixing methods have practical meaning in explaining spectral data of satellites and inversing satellite conditions.
2016, 45(S1): 127-131.
doi: 10.3788/IRLA201645.S123002
The characteristics of wheat protein content has high heritability, so fine-quality breeding can be achieved by selecting the high-protein wheat seed. Combined with chemometric methods' hyperspectral imaging technique was used to build the average model to achieve fast prediction of single wheat seed protein content. In the experiment, 47 unit wheat seed samples' hyperspectral images were collected by GaiaChem-NIR system, and the average spectra was obtained by image process methods. Then, synergy interval partial least squares was applied to select the characteristic spectral regions to optimize the prediction model of wheat seed protein content. The optimal models' determination coefficient is 0.94, the root mean square error of prediction is 0.28%, and the residual predictive deviation(RPD) is 3.30. Finally, the average model was applied to predict the protein content of each pixes of single wheat seed, and calculated the average as the single wheat grain protein content. The experimental results showed that different wheat grain's protein content value predicted by the optimal model existed difference. Ueanwhile, the prediction values varied around the average protein content of its sample, which reflected that the average model is accurate and feasible to predict single wheat grain's protein content. Therefore, the studied method provides a new way to select the high-protein wheat seed in the process of breeding, which can promote the development of wheat fine-quality breeding.
2016, 45(4): 423001.
doi: 10.3788/IRLA201645.0423001
The infrared spectrum of mixed gas got in the battlefield and complex environment results in overlapping and stagger of the primary and secondary peaks, so its feature extraction of qualitative recognition is particularly important. The infrared spectral data collected from a variety of chemical warfare agents and organic gases are high-dimensional data. Centralizing before reducing dimension was used for feature extraction to capture the essence of more information it contained. Since the infrared spectrum of the mixed gas was non-linear and non-Gaussian signal, this method regarded non-Gaussian as independence measure to separate each component as independent component. In order to meet real-time requirements, its iterative process was optimized based on the traditional fast independent component analysis(FastICA) algorithm and extreme learning machine(ELM) model was applied to quantitative analysis. Experiment results show that the iterations of optimized method reduces compared with the traditional method and mean square error of quantitative analysis is E=2.392 610-4 and regression coefficient is R=0.999. And the optimized method improves the isolated efficiency of separating pure substances spectra from mixture substances without affecting the separate accuracy.
2016, 45(4): 423002.
doi: 10.3788/IRLA201645.0423002
To extend the durability of timber, some research have been done on the timber factors' analysis and expression. Jujube timber, Northeast China ash timber, poplar timber are chosen as the samples, to measure the carbon-nitrogen content of the timbers and the lignin, analyze the ratio of carbon-nitrogen content as well; and to measure the lignin content, lignin density, water soluble lignin density, the extract content of soluble in benzene, alcohol solution and total extract density, compare the FTIR of timber and lignin, research the ratio of guaiacyl and syringyl. Results indicated that the air dry density of Jujube, the best durability timber, is 0.93 g/cm3, and as the FTIR of Jujube timber is 1 633 cm-1, during the stretching vibration of the carbonyl(C=O), there is wave crest existence. The value of G/S is 0.975, the nitrogen content of Jujube timber is 0.274% and nitrogen content of Jujube lignin is 0.444%, these values are the minimum compared with those of the other two timber samples. The carbon-nitrogen content ratio of Jujube timber and of Jujube lignin is respectively 180 and 135, the density of Jujube lignin is 184.39.7 mg/cm3, the total extract density is 88.13.5 mg/cm3, compared with Northeast China ash timber, poplar timber, these numerical values are the maximum.
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