A Review of Functional Near-Infrared Spectroscopy Studies of Motor and Cognitive Function in Preterm Infants.

Preterm infants are vulnerable to brain injuries, and have a greater chance of experiencing neurodevelopmental disorders throughout development. Early screening for motor and cognitive functions is critical to assessing the developmental trajectory in preterm infants, especially those who may have motor or cognitive deficits. The brain imaging technology functional near-infrared spectroscopy (fNIRS) is a portable and low-cost method of assessing cerebral hemodynamics, making it suitable for large-scale use even in remote and underdeveloped areas. In this article, we review peer-reviewed, scientific fNIRS studies of motor performance, speech perception, and facial recognition in preterm infants. fNIRS provides a link between hemodynamic activity and the development of brain functions in preterm infants. Research using fNIRS has shown different patterns of hemoglobin change during some behavioral tasks in early infancy. fNIRS helps to promote our understanding of the developmental mechanisms of brain function in preterm infants when performing motor or cognitive tasks in a less-restricted environment.

[Measurements of the concentration of atmospheric CO2 based on OP/FTIR method and infrared reflecting scanning Fourier transform spectrometry].

The present paper describes the observations and measurements of the infrared absorption spectra of CO2 on the Earth's surface with OP/FTIR method by employing a mid-infrared reflecting scanning Fourier transform spectrometry, which are the first results produced by the first prototype in China developed by the team of authors. This reflecting scanning Fourier transform spectrometry works in the spectral range 2 100-3 150 cm(-1) with a spectral resolution of 2 cm(-1). Method to measure the atmospheric molecules was described and mathematical proof and quantitative algorithms to retrieve molecular concentration were established. The related models were performed both by a direct method based on the Beer-Lambert Law and by a simulating-fitting method based on HITRAN database and the instrument functions. Concentrations of CO2 were retrieved by the two models. The results of observation and modeling analyses indicate that the concentrations have a distribution of 300-370 ppm, and show tendency that going with the variation of the environment they first decrease slowly and then increase rapidly during the observation period, and reached low points in the afternoon and during the sunset. The concentrations with measuring times retrieved by the direct method and by the simulating-fitting method agree with each other very well, with the correlation of all the data is up to 99.79%, and the relative error is no more than 2.00%. The precision for retrieving is relatively high. The results of this paper demonstrate that, in the field of detecting atmospheric compositions, OP/FTIR method performed by the Infrared reflecting scanning Fourier transform spectrometry is a feasible and effective technical approach, and either the direct method or the simulating-fitting method is capable of retrieving concentrations with high precision.

[Design and implementation of real-time processing platform for movement error correction of hyperspectrual imaging].

The approach that deals with compressed and packed image data transmitted from satellite to the ground is too slow for real-time application occasion, it also has huge image, multi-processing step and complexity recovery arithmetic synchronously, so it is urgent to build accurate and fast data processing platform for real-time processing. For the moment, the platform for data recovery and error correction is much less, the so-called successful platform may directly affect the effect of target detection and identification because of processing speed, precision, flexibility, configuration and upgrade. The platform we build is to set spatial modulation spectrometer as the research goal, We design and implement a hardware platform based on Xilinx Virtex-5 FPGA, It is combined with ISE IP soft-core resources which is configurable, high-precision and flexible by focusing on analyzing key aspects of the hardware platform. And the relevant test data were drawn, then a good way for spectrum recovery and error correction was explored.

[The melioration on spectra response heterogeneity of hadamard transform spectral imager].

Hadamard transform optics has been developed in the past decades. It has been used in distinguishing targets, detecting feeble signals and so on. Hadamard transform spectral imager (HTSI), based on digital micro-mirror device, is a new dispersion spectral imager. HTSI has been developed in our laboratory. The spectral heterogeneity of encoded image captured by HTSI has been researched according to spectrum calibration in this paper. Relative and absolute spectrum emittance calibration algorithms have been proposed first time on HTSI to meliorate the spectrum heterogeneity. It aims at the problem that the accuracy of recovered spectrum is depressed by the heterogeneity noise and disorder encoding spectrum in spectral image. Simulation and experiment result have demonstrated that the meliorated spectral curve is close to the standard spectrum, and the variance of the recovered spectrum ranges from 2.4% to 4.2% with regard to the spectral image of 7 waves. This is fully satisfied for the requirement of laboratory and projects.

[Research on endmember extraction algorithm based on spectral classification].

Spectral unmixing is an important task for data processing of hyperspectral remote sensing, which is comprised of extracting the pure spectra (endmember) and calculating the abundance value of pure spectra. The most efficient endmember extracting algorithms (EEAs) is designed based on convexity geometry such as pure pixel index (PPI), N-finder algorithm (N-FINDR). Most EEAs choose pure spectra from all pixels of an image so that they have disadvantages like slow processing speed and poor precision. Partial algorithms need reducing the spectral dimension, which results in the difficulty in small target identification. This paper proposed an algorithm that classifies the hyperspetral image into some classes with homogeneous spectra and considers the mean spectra of a class as standard spectra for the class, then extracts pure spectrum from all standard spectra of classes. It reduces computation and the effect of system error, enhancing the speed and precision of endmember extraction. Using the least squares with constraints on spectral extraction and spectral unmixing, by controlling the band average value of the maximum spectral redundant allowance to control the number of endmembers, does not need to reduce the spectral dimension and predetermine the number of endmembers, so compared to N-finder algorithm, such algorithm is more rational.

[General expression of optic path difference of reflecting rotating Fourier transform spectrometer].

The principle of reflecting rotating Fourier transform spectrometer was introduced in the present paper. Based on the Malus law and reflecting characteristic of cube corner, the optic path difference of reflecting rotating Fourier transform spectrometer was analyzed and calculated by choosing the center of rotating mirror as a reference point of the aplanatic surface of incidence beam and return beam. General expression of optic path difference at any time and maximal optic path difference of reflecting rotating Fourier transform spectrometer was presented. The factors that influence the maximal optic path difference and the period of optic path difference were analyzed. The results provide a theoretical guidance for design and manufacture of reflecting rotating Fourier transform spectrometer.

[Research on spectral classification algorithm based on spatial feature].

With the wide use of imaging spectroscopy, applying data cubes to classification and identification of materials has been developed to be an important research content. The classification algorithms play a vital role in accuracy and precision of object identification. The most common classification algorithms mainly make use of the information gained from spectral dimension and classify the materials based on spectral match. The material reflectance spectra collected by imaging spectroscopy is determined not only by the sorts, but also by the geometry structure and roughness of material surface, and so on. Then classification and identification algorithms only using the reflection spectra have errors to some extent. This paper puts forward an algorithm based on the common classification algorithms that controls the classification process by using the spatial feature of image to promote the correctness of classification. This algorithm was applied to identify the true leaves from the fake ones. The result shows preferable spatial continuity. To a great extent, the algorithm overcomes "ma pixel" domino effect, and is proved valid.

[Developments and trends of the computed tomography imaging spectrometers].

The present paper reviews the computed tomography imaging spectrometer (CTIS) measurement systems at home and abroad from the aspects of technological characterizations and research focuses. The developments of computed tomography imaging spectrometers are described, involving the adding new abilities by improving systematic structure and by incorporating other elements or systems, the study and applications of novel grating elements, detectors or apparatus, the optimizations and improvements of the system calibration methods and reconstruction algorithms. In addition, based on the classification of application scope, the extension status of probing spectral bands and application fields towards computed tomography imaging spectrometers and related systems are summarized. The principles of non-scanning computed tomography imaging spectrometer and high-throughput computed tomography imaging spectrometer are introduced. Moreover, the trends of computed tomography imaging spectrometers are discussed too.

[Comparison of correction methods for nonlinear optic path difference of reflecting rotating Fourier transform spectrometer].

The principle of reflecting rotating Fourier transform spectrometer was introduced in the present paper. The nonlinear problem of optical path difference (OPD) of rotating Fourier transform spectrometer universally exists, produced by the rotation of rotating mirror. The nonlinear OPD will lead to fictitious recovery spectrum, so it is necessary to compensate the nonlinear OPD. Three methods of correction for the nonlinear OPD were described and compared in this paper, namely NUFFT method, OPD replace method and interferograms fitting method. The result indicates that NUFFT was the best method for the compensation of nonlinear OPD, OPD replace method was better, its precision was almost the same as NUFFT method, and their relative error are superior to 0.13%, but the computation efficiency of OPD replace method is slower than NUFFT method, while the precision and computation efficiency of interferograms fitting method are not so satisfied, because the interferograms are rapid fluctuant especially around the zero optical path difference, so it is unsuitable for polynomial fitting, and because this method needs piecewise fitting, its computation efficiency is the slowest, thus the NUFFT method is the most suited method for the nonlinear OPD compensation of reflecting rotating Fourier transform spectrometer.

[Spatially modulated interference Hadamard transform spectral imager].

The principle and instrumental structure of dispersion Hadamard transform spectral imager were briefly described in the present paper, and the disadvantages of the imager both in dislocation of spatial and spectral information and in spectral resolution limited by the width of Hadamard encoding mask were pointed out. A new instrumental principle and design of spatially modulated interference Hadamard transform spectral imager was proposed. A lateral shearing interferometer was used to acquire interference signals of all the Hadamard encoding information at different optical path difference. Then the methods of Fourier transform and Hadamard transform for interferogram were performed to acquire the spectra of objectives. Theory analysis of this imager demonstrated that the modulation of interferogram would not be affected by some factors such as the form and size of Hadamard encoding mask, and the spectral resolution would not be influenced by the size of Hadamard encoding mask. Furthermore, such technique not only effectively eradicated the dislocation of spatial information and spectral information existing in dispersion Hadamard transform spectral imager, but also made it convenient to image with high-throughput, high spatial resolution and high spectral resolution.