南京理工大学电子工程与光电技术学院,江苏 南京 210094
由于白光干涉测量技术易受环境振动而产生干扰,提出了一种基于非均匀快速傅里叶变换(NUFFT)的抗振动白光干涉测量方法。该方法将白光干涉测量光路分为两个成像通道,首先通过准单色光干涉图求解移相间隔,通过移相间隔以及NUFFT算法对白光干涉图进行校正,最后利用校正的白光干涉图和七步移相算法复原出待测物体的三维形貌,实验结果表明,所提方法具有良好的抗振动性能。
测量 形貌测量 白光干涉 抗振动 非均匀快速傅里叶变换
1 上海理工大学光电信息与计算机工程学院,上海 200093
2 中国科学院上海光学精密机械研究所中科院空间激光传输与探测技术重点实验室,上海 201800
面向空间引力波探测对激光光源相对强度噪声的严苛需求,开展了极低相对强度噪声在低频段的测试表征技术研究。构建了基于低噪声光电探测器、高精度数字万用表以及快速傅里叶(FFT)频谱分析仪在低频段0.1 mHz~100 kHz的相对强度噪声测试系统。利用高精度数字万用表及FFT分段Smooth窗函数平滑算法实现对0.1 mHz~0.5 Hz的极低频段内相对强度噪声测试,本底噪声低于-99 dBc/Hz,同时利用低噪声放大器及FFT频谱分析仪测试在1 mHz~100 kHz的相对强度噪声,本底噪声低于-105 dBc/Hz。两种测试手段在1 mHz~0.5 Hz重叠频段内噪声测试结果的一致性验证了所构建测试系统在低频段测试结果的准确性。利用所构建的相对强度噪声测试系统对自研空间引力波探测用平面波导环形腔(NPRO)激光器、商用光纤激光器、商用外腔半导体激光器等多种激光器进行测试评估,并对其噪声成分及来源进行分析。所构建的低频段相对强度噪声测试系统可满足空间引力波探测对激光强度噪声评估的需求,同时也适用于其他低频段精密测量应用的激光光源噪声评估。
单频激光器 噪声测试 相对强度噪声 快速傅里叶变换 空间引力波探测 中国激光
2023, 50(23): 2301009
青岛科技大学自动化与电子工程学院,山东 青岛 266061
快速傅里叶变换是激光多普勒测速系统信号处理的一种常用方法,但在异步采样时存在频谱泄漏和栏栅效应,其处理精度偏低。为了提高检测精度,提出基于Nuttall窗函数和五项最大旁瓣衰减窗函数的混合卷积窗改进六谱线插值校正算法。混合卷积窗在保证良好的旁瓣特性的同时也能保证主瓣不过宽,改进六谱线插值可有效抑制栏栅效应在参数估计过程中的负面影响,提高分析精度。为了避免解高次方程,提出三次B样条插值来拟合插值系数,并推导出改进六谱线插值的频率校正公式。搭建了双光束后向散射差动式激光多普勒测速平台,利用仿真数据和实测信号验证了本文算法在低信噪比环境下有较好的频率和速度测量精度。
激光光学 快速傅里叶变换 激光多普勒测速 频谱泄漏 混合卷积窗 六谱线插值 三次B样条 激光与光电子学进展
2023, 60(17): 1714008
光学 精密工程
2023, 31(15): 2193
1 中国计量大学光学与电子科技学院,浙江 杭州 310018
2 杭州国照检测技术有限公司,浙江 杭州 310012
提出了一种在光纤距离方向作快速傅里叶变换(FFT)的振动信号相位提取方法,并在分布式声波传感(DAS)系统上加载200 Hz正弦信号进行了验证。该方法在振动传感光纤距离方向上采用分距离滑动FFT变换提取载波信号的相位,然后对光纤方向缠绕的相位信号进行差分,进而在光纤方向与时间方向上进行解缠绕处理,最后对解缠绕信号进行高通滤波。与DAS系统信号解调常用的IQ解调、希尔伯特变换解调相比,该方式提取的200 Hz振动信号的信噪比为36.71 dB,比IQ、希尔伯特变换提取的信噪比分别高21.04 dB和20.91 dB,且FFT提取的振动相位信号的周期性好,无谐波及低频噪声干扰。对2000 Hz和5000 Hz正弦振动信号的提取结果也表明该方式具有较好的适用性。
遥感 傅里叶光学 快速傅里叶变换 扰动检测 信号调制 信噪比
Author Affiliations
Abstract
1 Key Lab of Advanced Transducers and Intelligent Control System, Ministry of Education and Shanxi Province, College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, China
2 Department of Physics, Harbin Institute of Technology, Harbin 150001, China
3 Centre of Translational Atomaterials (CTAM), Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, VIC 3122, Australia
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The control of ultrafast optical field is of great interest in developing ultrafast optics as well as the investigation on various light-matter interactions with ultrashort pulses. However, conventional spatial encoding approaches have only limited steerable targets usually neglecting the temporal effect, thus hindering their broad applications. Here we present a new concept for realizing ultrafast modulation of multi-target focal fields based on the facile combination of time-dependent vectorial diffraction theory with fast Fourier transform. This is achieved by focusing femtosecond pulsed light carrying vectorial-vortex by a single objective lens under tight focusing condition. It is uncovered that the ultrafast temporal degree of freedom within a configurable temporal duration (~400 fs) plays a pivotal role in determining the rich and exotic features of the focused optical field at one time, namely, bright-dark alternation, periodic rotation, and longitudinal/transverse polarization conversion. The underlying control mechanisms have been unveiled. Besides being of academic interest in diverse ultrafast spectral regimes, these peculiar behaviors of the space-time evolutionary beams may underpin prolific ultrafast-related applications such as multifunctional integrated optical chip, high-efficiency laser trapping, microstructure rotation, super-resolution optical microscopy, precise optical measurement, and liveness tracking.
ultrafast optical field vectorial diffraction theory fast Fourier transform vectorial vortex beam space-time shaping Opto-Electronic Advances
2022, 5(3): 210026
Author Affiliations
Abstract
1 Fujian Key Laboratory of Ultrafast Laser Technology and Applications, School of Electronic Science and Technology, Xiamen University, Xiamen 361005, China
2 Wireless & Optoelectronics Research & Innovation Centre, Faculty of Computing, Engineering & Science, University of South Wales, Wales CF37 1DL, UK
Conventional wavelength modulation spectroscopy (WMS) is vulnerable to the influence of low-frequency noise. Accuracy of the method highly depends on the performance of the costly lock-in amplifier. In this article, we report a new and effective method for reconstructing second-harmonic signals through WMS based on fast Fourier transform (FFT). This method is less disturbed by low-frequency noise because it does not use a low-frequency ramp wave. Formulation and detection procedures were presented. The discrete second-harmonic waveform can be obtained by continuously changing the DC signal and FFT analysis in this method. Second-harmonic waveforms acquired by the two means are generally consistent. The experimental study validates the obtained gas concentration from 5% to 30%, showing a good linear relationship by the proposed method. The maximum relative error on concentration extraction is 2.87%; as for conventional WMS, this value is 4.50%. The developed measurement method may have potential in computed tomography.
fast Fourier transform wavelength modulation spectroscopy second-harmonic waveform Chinese Optics Letters
2022, 20(9): 093001
国防科技大学电子科学学院,湖南 长沙 410073
本文提出了一种一端固定的双站SAR(OS-BiSAR)体制下基于距离补偿的毫米波快速成像算法。在图像重构过程中,该算法通过保留回波模型中的幅度衰减因子来补偿信号传播衰减,并根据目标回波方程特性对接收阵列维执行了卷积操作,最后通过快速傅里叶变换(FFT)以及相干累加等步骤求解出最终目标图像。仿真分析和实验结果表明,与OS-BiSAR体制下基于距离补偿的距离徙动算法(RMA)相比,所提算法不仅可以保证图像重构效率,还能更显著地降低信号沿空间路径的传播损耗对成像质量带来的影响。
毫米波快速成像算法 距离补偿 一端固定的双站SAR 快速傅里叶变换 millimeter-wave fast imaging algorithm range compensation one-stationary bistatic synthetic aperture radar(OS-BiSAR) fast Fourier transform(FFT)
江西理工大学电气工程与自动化学院,江西 赣州 341000
近年来,基于深度学习的高光谱图像(HSI)分类研究引起了各领域的广泛关注。HSI光谱波段数多、信息冗余度高、计算复杂,出现训练样本不足的问题,容易导致模型训练过拟合,影响分类精度。为了提高分类精度并减少训练时间,提出一种基于三维卷积神经网络(3D-CNN)并结合双分支双注意力机制的快速密集连接网络,用于HSI的分类。首先利用主成分分析(PCA)对原始数据进行降维,减少冗余信息,然后采用双分支密集连接结构,并结合快速傅里叶变换(FFT)的双分支高效通道注意力(ECA)机制,同时增加了一个FFT层,既保证了模型的分类精度,也加快了模型的训练速度。在多个公共高光谱数据集上对方法进行实验验证,性能评估指标采用总体分类精度(OA),平均分类精度(AA)和Kappa系数。实验结果表明,所提方法在提高分类精度的同时,显著减少了训练时间和测试时间。
图像处理 高光谱图像分类 主成分分析 密集连接 双注意力机制 快速傅里叶变换 激光与光电子学进展
2022, 59(8): 0810002