Total annoyance from an industrial noise source with a main spectral component combined with a background noise

When living close to an industrial plant, people are exposed to a combination of industrial noise sources and a background noise composed of all the other noise sources in the environment. As a first step, noise annoyance indicators in laboratory conditions are proposed for a single exposure to an industrial noise source. The second step detailed in this paper involves determining total annoyance indicators in laboratory conditions for ambient noises composed of an industrial noise source and a background noise. Two types of steady and permanent industrial noise sources are studied: low frequency noises with a main spectral component at 100 Hz, and noises with a main spectral component in middle frequencies. Five background noises are assessed so as to take into account different sound environments which can usually be heard by people living around an industrial plant. One main conclusion of this study is that two different analyses are necessary to determine total annoyance indicators for this type of ambient noise, depending on the industrial noise source composing it. Therefore, two total annoyance indicators adapted to the ambient noises studied are proposed.     

Active spectral filtering through turbid media

We demonstrate controlled wavelength-dependent light focusing through turbid media using wavefront shaping. Due to the dispersion caused by multiple light scattering, light propagation through turbid media can be independently controlled between different wavelengths. Foci with various wavelengths can be generated by applying different optimized wavefronts to a highly scattering layer. Given the linearity of the transmission matrix, multiple foci with different wavelengths can also be simultaneously constructed.     

Experimental characterization of simultaneous spatial and spectral filtering by an optical resonant filter

Simultaneous spatial and spectral filtering by an optical resonant filter has been characterized experimentally to furnish additional insight into the operation and applications of optical resonant filters. Our experimental study can be useful for applications that depend on spatial filtering, spectral filtering, spatial-spectral filtering, and polarization selectivity. One significant application is the integration of an optical resonant filter with semiconductor lasers to control the spatial-spectral radiation for optimum performance.     

Modified LACIF filtering in background disjoint noise

This work deals with pattern recognition methods based on correlations for images in the presence of noise. We propose a modification of the nonlinear Locally Adaptive Contrast Invariant Filter (LACIF) that yields correlation peaks that are invariant to linear intensity changes of the target but that has some limitations in the presence low variance nonoverlapping background noise. The modification of the filter implies a normalization by a global variance of several distributions. The estimation of the variance distributions is done locally by means of correlations. Experimental results as well as comparisons with the classical matched filter and the common LACIF are given.     

OPCPA pump laser based on a regenerative amplifier with volume Bragg grating spectral filtering

A novel Nd:YVO₄−based regenerative amplifier system operating in the picosecond regime featuring a volume Bragg grating (VBG) as an intracavity spectral narrowing element is described. This compact amplifier provides pulses with duration of ∼85 ps operating at repetition rates ranging from single shot to 10 kHz. The VBG is used to passively tailor the pulse duration and achieve transform-limited pulses with 50 pm FWHM of spectral linewidth. A Gaussian output beam profile is obtained from the amplifier at all repetition rates. The intracavity VBG also guarantees a high spectral purity by efficiently preventing the build-up of out-of-band ASE. The spectral, spatial and temporal properties of this amplifier make it highly suitable for OPCPA pumping applications.     

Adaptive time-domain filtering for real-time spectral discrimination in a Michelson interferometer

We present a method of spectral discrimination that employs time-domain processing instead of the typical frequency-domain analysis and implement the method in a Michelson interferometer with a nonlinear mirror scan. The technique yields one analog output value per scan instead of a complete interferogram by directly filtering a measured scan with a reference function in the time domain. Such a procedure drastically reduces data-processing requirements downstream. Additionally, using prerecorded interferograms as references eliminates the need to compensate for scan nonlinearities, which broadens the field of usable components for implementation in miniaturized sensing systems. With our efficient use of known spectral signatures, we demonstrate real-time discrimination of 633- and 663-nm laser sources with a mirror scan length of 1 microm , compared with the Rayleigh criterion of 7 microm.     

Optimization of ultrashort-pulse squeezing by spectral filtering with the Fourier pulse-shaping technique

We propose an adaptive waveform-control approach to optimize photon-number squeezing by the nonlinear fiber spectral filtering method. More than -8-dB squeezing of the sech envelope pulse is numerically predicted when the spectral phase is modulated before the pulse is sent to a fiber. The quantum cross correlations of the photon-number fluctuation become uniformly negative when the pulse is optimally shaped.     

结合背景差分和显著值筛选的运动检测算法

本文为降低背景干扰,提出了一种结合背景差分和显著值筛选的运动检测方法。该方法将VIBE运动检测方法看作一个前置处理过程,用于粗定位可疑目标区域。然后在这些可疑目标区域上,提出一种基于稀疏表示和组合Lasso回归的显著值计算方法,计算可疑区域图像块的显著值。最后通过滤除显著值过小的可疑区域图像块来降低背景干扰,提高运动检测的精确度指标。在Changedetection.net的数据子集上的仿真实验结果表明,该方法的召回率和精确度指标都较高,而且平均检测耗时少。     

Detecting and filtering a flow of different pulsed signals against the noise background

We consider the problem of separate detection and filtration of a flow of pulsed signals. We assume that statistically independent pulsed signals of different shape and random amplitude appear randomly against the background of noise. An algorithm for estimation of the detection probability of each signal is obtained. Recurrent expressions for thea posteriori probability density of each signal are found. The results of numerical simulation of the proposed algorithms of signal processing are presented. Lobachevsky State University of Nizhny Novgorod Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 1, pp. 92–100, January, 1999.     

Optical image encryption with multistage and multichannel fractional Fourier-domain filtering

We present a novel image-encryption algorithm that employs multichannel and multistage fractional Fourier-domain filtering architecture. We perform the encryption and decryption by randomly filtering the spatial frequency of the image and then recombining the information from the algorithm in a multistage fractional Fourier domain with pure random-intensity-encoded masks and their complements in a multichannel scheme. The algorithm can be implemented iteratively in an electro-optical setup. Numerical simulations have verified the validity of the algorithm.     

滤波位置相关的全正色散掺Yb3+锁模光纤激光器的实验研究

采用非线性偏振旋转锁模,构建了一种全正色散掺Yb³⁺光纤环形激光器.在该激光腔内采用了10 nm带宽的光纤滤波器提供附加的自振幅调制.通过改变滤波器在腔内的位置,实验证明了滤波器位置对高啁啾脉冲的整形过程起到重要的作用.在320 mW的抽运功率下,最终获得平均功率为922 mW,脉冲重复频率为266 MHz,脉冲宽度为62 ps的稳定脉冲输出,单脉冲能量达35 nJ的优化结果.通过数值模拟与实验结果的验证表明,两者相符很好. 关键词： 锁模光纤激光器 全正色散 滤波效应 高啁啾脉冲     

Artificial spectral filtering in dissipative soliton fiber lasers with invisible bandpass filters

We numerically study the artificial spectral-filtering effect in dissipative soliton fiber lasers without intracavity spectral filters. It is found that in dissipative soliton lasers with real saturable absorbers (SAs), the dynamic spectral filtering of the real SAs serves as an artificial spectral filter and contributes to the pulse shaping. While in the dissi- pative soliton lasers with artificial SAs, such as nonlinear polarization rotation, the spectral filtering introduced by the intracavity polarization-dependent components acts as an artificial spectral filter and shapes the pulses to obtain mode-locking. An investigation of the artificial spectral-filtering effect reveals the operating mechanisms of the dissipative soliton fiber lasers without visible bandpass filters.     

静态计算光谱成像仪图谱反演的关键数据处理技术

静态计算光谱成像技术中图谱反演环节是实现其理论优势极为关键的一步, 是决定最终获得图谱质量优劣的数据处理技术. 本文为此专注于计算光谱的图谱反演环节,对图像压缩感知理论算法、图像重构算法、 以及针对图谱三维数据的反演算法都开展了深入的研究和比较, 并结合所研制系统的图谱数据传输全链路和工程研制过程中误差等因素进行全面详尽的仿真验证, 给出各种图谱反演算法验证、分析结果. 指出静态计算光谱成像系统研制中图谱反演环节的关键数据处理问题,适合采用的算法及其优化路线. 为顺利研制静态计算光谱成像仪,保证其理论优势的实现,提供了详实的分析、参考依据. 关键词： 计算光谱 编码孔径 压缩感知 图谱反演     

Single femtosecond exposure recording of an image hologram by spectral hole burning in an unstable tautomer of a phthalocyanine derivative

We demonstrate, for what we believe is the first time, recording of a femtosecond image hologram by illumination with a single pair of high-intensity femtosecond pulses in a broad inhomogeneous bandwidth spectral hole-burning material consisting of a polymer film doped with anthraceno-phthalocyanine dye molecules. High efficiency of spectral hole burning is achieved by preillumination of the sample at a low temperature to convert the dye molecules into an unstable tautomer form.     

基于图像复原的高光谱图像前向像移补偿

为了提高高光谱图像空间维的图像分辨力,针对航空遥感器成像时由前向像移造成的图像模糊提出了像移补偿方法。分析了航空遥感器前向像移造成图像模糊的退化机制,对运动模糊图像进行了预处理;估计了点扩散函数和噪声功率,使用改进的维纳滤波算法对图像进行复原并以绝对平均误差、峰值信噪比作为评价标准进行了实验。在估计出模糊图像点扩散函数和噪声功率的情况下得到的结果显示:与传统的维纳滤波复原算法相比,改进的维纳滤波复原算法的图像绝对平均误差降低了9.31%,峰值信噪比提高了13.98%,表明提出的算法能够有效改善高光谱图像的像质。     

光谱滤波技术对星等测量精度的影响

白天对空间目标进行观测时,采用光谱滤波技术可以提高光电系统的极限星等探测能力。针对光谱滤波探测特点,基于现有测量方法,结合光谱反射特性,分析了光谱滤波技术对测量精度的影响,给出了修正方法;利用光电系统对某空间目标进行了实际测量,根据事后修正方法进行了仿真研究,对实际测量值与事后修正值进行了比对分析。分析表明：光谱滤波技术虽然提高了光电系统的探测能力,但对测量精度带来了较大的影响,最大精度可为0.5等星。     

光谱滤波技术对星等测量精度的影响

 白天对空间目标进行观测时,采用光谱滤波技术可以提高光电系统的极限星等探测能力。针对光谱滤波探测特点,基于现有测量方法,结合光谱反射特性,分析了光谱滤波技术对测量精度的影响,给出了修正方法;利用光电系统对某空间目标进行了实际测量,根据事后修正方法进行了仿真研究,对实际测量值与事后修正值进行了比对分析。分析表明：光谱滤波技术虽然提高了光电系统的探测能力,但对测量精度带来了较大的影响,最大精度可为0.5等星。