高光谱成像技术在果蔬品质与安全无损检测中的原理及应用

水果和蔬菜的品质与安全是消费者最为关心的问题。传统的化学检测方法是一种费时费力的破坏性检测技术。随着成像和光谱技术的快速发展,高光谱成像技术已经广泛应用于农产品品质与安全的快速无损检测中。高光谱成像技术融合了传统的成像和光谱技术的优点,可以同时获取被检测物体的空间信息和光谱信息,因此该技术既可以像检测物体的外部品质,又可以像光谱技术一样检测物体的内部品质和品质安全。目前,已经有大量的基于高光谱成像技术检测水果和蔬菜品质与安全的研究性论文发表,为了深入了解高光谱成像技术的检测原理并跟踪国内外最新的研究进展,综述了高光谱成像技术在水果和蔬菜外部品质、内部品质和品质安全检测中的原理、发展和应用。另外,还简要介绍和讨论了高光谱成像系统的构成、常用的数据分析方法、发展趋势及面临的挑战。     

高光谱图像技术在农产品检测中的应用进展

综述了高光谱图像技术在农产品品质和食用安全性检测方面的研究现状及其在无损检测中的应用进展.在此基础上,提出了利用高光谱图像技术检测农药残留的解决途径,对高光谱图像技术在生物医学信息检测和农药残留检测中的应用前景进行了展望,指出高光谱图像技术是生物组织功能信息分析的一种新方法,是符合我国农产品产销特点的农药残留检测的潜力技术,可保障农产品质量和安全.     

近红外光谱检测技术在害虫检测中的应用

近红外光谱是20 世纪80 年代以来发展最快、最引人注目的光谱分析技术。以其快速、无损伤、操作简单、稳定性好、效率高等特点,在仓储害虫检测、种子害虫侵染检测和林草害虫危害检测中的应用已成为一个活跃的研究领域。而近红外光谱技术在我国害虫检测中的研究和应用则较少,处于刚刚起步阶段。因此,文章介绍了利用近红外光谱技术检测的基本原理, 综述了国内外利用近红外光谱技术检测农林业害虫的应用情况,并对近红外检测技术在害虫检测上的应用进行了展望,以期推动近红外光谱技术在我国害虫检测科技和生产中的应用。     

非球面光学元件的面形检测技术

介绍了非球面各加工阶段的面形检测技术及其最新进展,重点介绍了非球面精密抛光期的面形检测技术,并对其中的非零位子孔径拼接干涉检测法和部分补偿法进行了详细阐述,提出了适用于大口径、深度非球面面形检测的组合干涉法的概念。概述了近年来受到关注的自由曲面非球面的发展和检测技术现状,展望了非球面检测技术的发展趋势。     

非球面光学元件的面形检测技术

介绍了非球面各加工阶段的面形检测技术及其最新进展,重点介绍了非球面精密抛光期的面形检测技术,并对其中的非零位子孔径拼接干涉检测法和部分补偿法进行了详细阐述,提出了适用于大口径、深度非球面面形检测的组合干涉法的概念。概述了近年来受到关注的自由曲面非球面的发展和检测技术现状,展望了非球面检测技术的发展趋势。     

总磷在线检测技术的探索

水中磷的含量是水质检测中的一个重要指标,目前还没有一种准确、快速、环保、便捷的总磷在线检测技术。因此,许多科技工作者为了实现这个目标从各个技术领域展开研究,并且取得了一定的成果,推动了总磷在线检测技术的发展。结合国内外总磷检测技术中的流动注射分光光度法、离子色谱法、化学传感器、近红外光谱、电感耦合等离子体-原子发射光谱法等总磷检测技术的优缺点和发展状况,对总磷在线检测技术进行了简要的介绍和探讨。     

星载成像光谱仪杂散光检测技术

介绍了星载成像光谱仪杂散光检测技术在国内外的发展状况,阐述了成像光谱仪杂散光的定义、来源和危害,分析了杂散光检测的必要性。通过截止滤光片法、光谱法、谱杂散光系数法、级数透过率法、氧气吸收光谱及参数拟合法、卷积计算法和矩阵修正法等7种光谱仪器杂散光检测方法优缺点的对比,给出了星载成像光谱仪杂散光检测技术的具体要求和发展趋势,认为单一的检测技术很难满足工程研制的实际需要,针对各研制阶段的组合检测技术将是星载成像光谱仪杂光检测的发展方向。     

水源性病原菌光谱检测技术研究进展

水源性病原菌污染会引发多种疾病,严重危害人类健康和公共卫生安全。水源性病原菌检测对人类医疗保健、水安全保障和疾病诊断等具有重要的意义。常规水源性病原菌检测技术,如人工培养法、分子生物法和免疫学法,其测量结果准确、有效,但样品预处理繁琐且费时,不利于病原菌实时在线检测。光谱检测技术以非侵入式获取病原菌发射、散射或吸收光谱特征,能够确定病原菌性质、结构和含量等信息。由于该技术具有易于操作、快速、便携、无损和便于实时监测等优点,在环境监测、生物分析中具有广泛的应用前景。文章介绍了现有水源性病原菌检测技术及其优缺点,指出开展病原菌快速、高效检测的必要性;讨论了光谱检测技术原理及数据分析方法,重点综述了紫外可见光谱、荧光光谱、红外光谱、拉曼光谱和太赫兹光谱在水源性病原菌检测的工作原理和研究进展;最后总结了各技术的优缺点。提出了光谱技术在病原菌检测的实际应用中面临的挑战及应对策略,为进一步发展基于光谱技术的水源性病原菌的快速检测提供参考。     

食品中三聚氰胺的光谱检测与分析技术研究进展

三聚氰胺是豆、乳类制品中的非法食品添加剂,曾作为蛋白质的廉价代替物被非法添加进奶粉等食品中,造成了严重的社会危害,极大地威胁人民生命财产安全。目前光谱技术已成为识别和定量检测非法食品添加剂的有效手段,为质量监管部门提供了可靠的研究方法和鉴定依据。光谱检测技术的时效性、无损性和准确性提高了食品中三聚氰胺的检测效率,促进了精准化、自动化食品质量检测的发展。近年来有大量研究围绕着三聚氰胺的光谱检测新技术,如开发新型增强底物或传感器,降低三聚氰胺的检测限,提高检测精度;开发更加便携的自动化光谱快检设备,降低检测成本,提高检测效率。这些光谱技术各具优势,但很难形成标准化、统一化的检测规范,使得各种光谱检测技术仅仅停留在试验阶段,无法应用于实战。另一方面,随着人工智能与模式识别技术的发展,光谱数据分析方法在近年来也有着长足的进步,各种光谱预处理和数据建模方法被不断提出,大大提高了光谱检测技术的灵敏性和稳定性。综述了近十年光谱技术（拉曼光谱、近红外光谱、荧光光谱、光谱成像等）在三聚氰胺检测中的应用现状,总结了不同仪器检测限、定量范围和样品前处理方法;分析了各种光谱预处理和光谱数据建模方法在不同光谱数据中的适用性,归纳出这些方法的优劣与适配的仪器,并对其应用前景和研究趋势进行了展望。     

声发射技术在铁路系统检测中的研究和应用

高速铁路的快速发展,给我国经济和社会发展带来了巨大的推动作用,同时对铁路系统的安全性提出了更高的要求。针对声发射技术在铁路系统安全检测中的研究和应用,介绍了声发射技术及其在检测应用中的优点,综述了目前国内外声发射技术在铁路系统检测研究中的情况,包括钢轨伤损检测、车轮伤损检测、轮轴轴承伤损检测、铁路结构安全监测以及车体材料安全监测等,特别针对钢轨裂纹伤损引起的钢轨断裂这一铁路安全中的主要事故,着重分析了声发射技术在钢轨裂纹伤损检测研究中的情况,并介绍了在高速铁路方面的应用探索。最后在上述分析总结的基础上,指出了声发射技术在铁路系统特别是高速铁路检测研究中的前景及研究难点。     

Dipolar and quadrupolar detection using an FT-ICR MS setup at the MPIK Heidelberg

Dipolar and single-phase two-electrode quadrupolar detection schemes have been investigated at a Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) setup built for the KATRIN experiment at the Max-Planck-Institute for Nuclear Physics (MPIK) in Heidelberg. We present first experimental results of ⁷Li^?+? signals from a cylindrical Penning trap configuration for both detection schemes. While the prominent signal of the conventional dipolar detection scheme marks the reduced cyclotron frequency, the main signal for the quadrupolar detection appears at the sum of the reduced cyclotron frequency and the magnetron frequency. For ideal trapping fields, this sum frequency equals the ion cyclotron frequency ?? _c ?=?qB/(2??m). Sidebands due to the combined motions of the cyclotron mode and magnetron mode are observed by quadrupolar detection which allows the determination of the respective combinations of eigenfrequencies.     

Analysis of atmospheric effects on the continuous variable quantum key distribution

Atmospheric effects have significant influence on the performance of a free-space optical continuous variable quantum key distribution (CVQKD) system. In this paper, we investigate how the transmittance, excess noise and interruption probability caused by atmospheric effects affect the secret-key rate (SKR) of the CVQKD. Three signal wavelengths, two weather conditions, two detection schemes, and two types of attacks are considered in our investigation. An expression aims at calculating the interruption probability is proposed based on the Kolmogorov spectrum model. The results show that a signal using long working wavelength can propagate much further than that of using short wavelength. Moreover, as the wavelength increases, the influence of interruption probability on the SKR becomes more significant, especially within a certain transmission distance. Therefore, interruption probability must be considered for CVQKD by using long-signal wavelengths. Furthermore, different detection schemes used by the receiver will result in different transmission distances when subjected to individual attacks and collective attacks, respectively.     

Signal detection without finite-energy limits to quantum resolution

We show that there are extremely simple signal detection schemes where the finiteness of energy resources places no limit on the resolution. On the contrary, larger resolution can be obtained with lower energy. To this end the generator of the signal-dependent transformation encoding the signal information on the probe state must be different from the energy. We show that the larger the deviation of the probe state from being the minimum-uncertainty state, the better the resolution.     

Temporal filtering with fast ICCD cameras in Raman studies

A common problem when applying Raman scattering in applied research is spectral interference from laser‐induced fluorescence. Extensive work has been invested in developing spectral and polarization filters as well as modulation schemes to refine spontaneous Raman signals. This current work, however, focuses on utilizing the temporal domain using a picosecond laser system and ICCD cameras with relatively short decay of the camera gate to prevent the fluorescence tail from being captured in Raman experiments. Further, the approach of using an ICCD camera to perform temporal filtering is compared to earlier proposed detection schemes using streak cameras or Kerr gates. The temporal‐filtering scheme is evaluated in a spectroscopic investigation where a background subtraction algorithm is presented. The temporal‐filtering scheme was also evaluated for Raman imaging of a levitated water droplet surrounded by fluorescing toluene vapor. Furthermore, the temporal‐filter detection scheme was simulated in order to provide straight forward evaluation tools to estimate the potential of performing temporal filtering with a laser/camera system considering: laser‐pulse duration, time jitter, camera‐gate characteristics, gate delay times, fluorescence lifetimes, and relative signal strength between the Raman and fluorescence signal. The fluorescence signal was modeled with a closed two‐level system, and the simulated results were compared to results from an investigation of the rising slope of toluene fluorescence. These evaluation tools and experimental investigations may serve as guidelines for planning and performing Raman measurements in situations where traditional filter‐rejection schemes are insufficient. Copyright © 2013 John Wiley & Sons, Ltd.     

Displacement- and timing-noise-free gravitational-wave detection

Motivated by a recently invented scheme of displacement-noise-free gravitational-wave detection, we demonstrate the existence of gravitational-wave detection schemes insusceptible to both displacement and timing (laser) noises and are thus realizable by shot-noise-limited laser interferometry. This is possible due to two reasons: first, gravitational waves and displacement disturbances contribute to light propagation times in different manners; second, for an N-detector system, the number of signal channels is of the order Omicron(N(2)), while the total number of timing- and displacement-noise channels is of the order Omicron(N).     

Retrodiction for coherent communication with homodyne or heterodyne detection

Previous work on the retrodictive theory of direct detection is extended to cover the homodyne detection of coherent optical signal states and . The retrodictive input state probabilities are obtained by the application of Bayes' theorem to the corresponding predictive distributions, based on the probability operator measure (POM) elements for the homodyne process. Results are derived for the retrodictive information on the complex amplitude of the signal field obtainable from the difference photocount statistics of both 4-port and 8-port balanced homodyne detection schemes. The local oscillator is usually assumed much stronger than the signal but the case of equal strengths in 4-port detection is also considered. The calculated probability distributions and error rates are illustrated numerically for values of signal and local oscillator strengths that extend from the classical to the quantum regimes.     

2D single-shot imaging of OH radicals using tunable excimer lasers

Three schemes for imaging OH with tunable excimer lasers are compared: Excitation and detection at 308 nm (0–0 band, XeCl laser), excitation with a KrF laser at 248 nm (3–0 band) and a new scheme using excitation at 308 nm and detection at 343 nm (0–1 band). Each scheme has certain advantages: The first scheme gives by far the highest signal, the second is less sensitive to collisional quenching and the third is suited to dirty environments because of the long excitation wavelength and off-resonance detection.     

Squeezed states in direct and coherent detection

With reference to squeezed states, we analyse the noise performances of the basic detection schemes in fibre telecommunications and interferometry. We have developed a semiclassical approach that allows us to translate the quantum mechanical formalism into synthetic expressions and rules only involving directly measurable physical quantities. As a result, we find that in the telecommunication field squeezed states do not allow significant improvements in system performances: in practice, the signal-to-noise ratio cannot be increased in standard detection schemes, both direct and coherent, by squeezing either the signal (because of propagation losses) or by the local oscillator. On the contrary, a significant improvement can be obtained in interferometric measurements if squeezed vacuum is coupled into the normally unused beamsplitter port.     

Iterative joint data detection and channel estimation for uplink MC-CDMA systems in the presence of frequency selective channels

This paper is concerned with joint multiuser detection and multichannel estimation (JDE) for uplink multicarrier code-division multiple-access (MC-CDMA) systems in the presence of frequency selective channels. The detection and estimation, implemented at the receiver, are based on a version of the expectation maximization (EM) algorithm and the space-alternating generalized expectation–maximization (SAGE) which are very suitable for multicarrier signal formats. The EM-JDE receiver updates the data bit sequences in parallel, while the SAGE-JDE receiver reestimates them successively. The channel parameters are updated in parallel in both schemes. Application of the EM-based algorithm to the problem of iterative data detection and channel estimation leads to a receiver structure that also incorporates a partial interference cancelation. Computer simulations show that the proposed algorithms have excellent BER end estimation performance.     

Simulation-based comparison of noise effects in wavelength modulation spectroscopy and direct absorption TDLAS

A simulative investigation of noise effects in wavelength modulation spectroscopy (WMS) and direct absorption diode laser absorption spectroscopy is presented. Special attention is paid to the impact of quantization noise of the analog-to-digital conversion (ADC) of the photodetector signal in the two detection schemes with the goal of estimating the necessary ADC resolution for each technique. With laser relative intensity noise (RIN), photodetector shot noise and thermal amplifier noise included, the strategies used for noise reduction in direct and wavelength modulation spectroscopy are compared by simulating two respective systems. Results show that because of the combined effects of dithering by RIN and signal averaging, the resolutions required for the direct absorption setup are only slightly higher than for the WMS setup. Only for small contributions of RIN an increase in resolution will significantly improve signal quality in the direct scheme.