1 河北工业大学 电子信息工程学院，天津 300401
2 电磁空间安全全国重点实验室，天津 300308
红外图像可在低照度、恶劣天气等条件下工作，红外车辆检测技术旨在使用红外传感器来监测道路上的车辆，实现对车辆数量、车速等信息的收集与分析，该技术不仅可应用于路面车辆，还可应用于铁路、机场、港口等场景，为交通运输行业的安全和便捷提供了有效的技术支持。然而，由于红外图像成像原理的局限和外部环境的干扰，通常导致红外图像成像质量不理想，红外车辆检测仍然存在许多问题。文中提出了一种改进的YOLOv5模型，在YOLOv5的主干部分引入了混合注意力机制，使模型能够更好地关注研究者感兴趣的区域，抑制图像噪声的干扰。此外，在BiFPN基础上提出了一种改进的Z-BiFPN特征融合结构，融合更多的浅层信息，提高浅层信息利用率，并增加一个四分之一下采样的小目标检测层，同时将YOLOv5的检测头替换为解耦头来提升模型的检测能力。在自建的七类红外车辆数据集INFrared-417上进行了实验，验证了算法的有效可行性。与原始YOLOv5相比，mAP从81.1%提升到了85.3%。
红外车辆 目标检测 注意力机制 特征融合 YOLOv5 infrared vehicle object detection attention mechanism feature fusion YOLOv5 红外与激光工程
2023, 52(8): 20230245
夏菁 1,2,3江俊峰 1,2,3,*王双 1,2,3丁振扬 1,2,3[ ... ]刘铁根 1,2,3
1 天津大学精密仪器与光电子工程学院，天津 300072
2 天津大学光电信息技术教育部重点实验室，天津 300072
3 天津大学光纤传感研究所天津市光纤传感工程中心，天津 300072
研究了基于光纤缠绕薄壁圆筒的声增敏方法，基于33耦合器建立了声压灵敏度标定实验系统，实验探讨了薄壁圆筒的方向特性，实验研究了半径、壁厚尺寸参数对光纤声增敏的影响，实现的声压灵敏度达到1.338 rad/Pa（-117.47 dB re rad/μPa）。光纤缠绕薄壁圆筒接入所搭建的准分布式声传感系统进行实验，在20.06 km传感距离上，恢复的1 kHz正弦波形与施加波形误差不超过4.1%，比未增敏光纤环传感信噪比提高了21.03 dB，显示了薄壁圆筒声增敏的传感效果。该研究结果为高灵敏度的准分布式声传感的进一步发展提供了实验基础。
光纤光学与光通信 光纤传感器 分布式声传感 光纤光学 薄壁圆筒 相位 激光与光电子学进展
2023, 60(7): 0706003
石家庄铁道大学材料科学与工程学院, 石家庄 050043
为构筑高效纸型催化剂用于碳烟消除, 如何设计不同活性基元并实现与基体纤维的协同效应非常重要。通过静电纺丝法制备了一系列La1-xKxMnO3(x=0、0.1、0.2、0.3、0.4、0.5)纳米纤维催化剂, 并以其为基元制备了纸型催化剂用于碳烟催化消除。采用X射线衍射仪、扫描电子显微镜、X射线光电子能谱以及程序升温还原等表征手段分析了纳米纤维催化剂中离子掺杂导致活性变化的原因, 并进行了碳烟氧化性能评价。结果表明: 所有的纳米纤维催化剂均呈现单一的钙钛矿结构, 当x≥0.3时, 样品中出现新相K2Mn4O8。样品中活性氧的数量是由K+置换La3+和Mn3+→Mn4+ 2个方面因素造成的。A位离子的置换增加了体系中氧缺陷程度, 但是高含量K的引入引发新相的形成, 使得体系中Mn3+→Mn4+开始占据主导地位, 氧空位数量逐渐增加。样品La0.6K0.4MnO3具有最佳的催化活性, 其T50为347 ℃。将纳米纤维与莫来石纤维按1:1比例制备的纸型催化剂活性最佳, T50为478 ℃。
锰酸镧 纳米纤维 纸型催化剂 碳烟氧化 lanthanum manganate nanofibers paper catalysts soot oxidation
Author Affiliations
Abstract
A refractive index (RI) sensor based on perfluorinated plastic optical fiber (PF-POF) is introduced in this paper. The PF-POF as multi-mode fiber was side-polished (SP) to form a macro-bending single-mode-multimode-single-mode (SMS) structure. Both ends of the sensor were closely connected to single-mode quartz optical fiber (SMF). The spectral characteristics of the sensor are measured, analyzed and discussed. The results show that when the length of PF-POF is 8 cm, the macro-bending radius is 3 cm, and the SP-depth is 20 μm. The intensity sensitivity reaches -219.504 dBm/RIU in the range of RI = 1.330 ~ 1.356. A reference is provided for the application of PF-POF in RI sensor in the future. The sensor is featured with low-cost, good flexibility and high efficiency.
Opto-Electronic Advances
2021, 4(10): 200041-1
Xuezhi Zhang 1,2,3Guanlong Chen 1,2,3Junfeng Jiang 1,2,3,*Xiaojun Fan 1,2,3[ ... ]Tiegen Liu 1,2,3,**
1 School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China
2 Tianjin Optical Fiber Sensing Engineering Center, Institute of Optical Fiber Sensing of Tianjin University, Tianjin 300072, China
3 Key Laboratory of Opto-Electronics Information Technology (Tianjin University), Ministry of Education, Tianjin 300072, China
4 Beijing Institute of Structure and Environment Engineering, Beijing 100076, China
In this paper, a weak fiber Bragg grating (WFBG) based sensing system applied to the cryogenic static test of launch vehicle oxygen tanks has been developed and the results of an evaluation are reported. A customized sensor encapsulation and installation method allow for precise strain measurement at cryogenic temperatures. The reflection peaks of series-connected WFBGs with low optical loss are obtained, ensuring high system reliability in harsh environments. The experimental results show that the maximum full-scale error is less than 0.81% full-scale error. The temperature is as low as -193 °C during the test. This study also demonstrates a practical method in which WFBG can be used to obtain critical parameters for structural monitoring in a cryogenic environment.
fiber optics weak fiber Bragg grating cryogenic static test oxygen tank strain 激光与光电子学进展
2021, 58(21): 2136001
烟台大学光电信息科学技术学院, 山东 烟台 264005
单像素成像的图像复原依赖于单像素接收信号和调制光源的关联,包括计算鬼成像和压缩感知成像两种方案。其中,计算鬼成像利用光源和单像素信号之间的高阶强度关联函数复原图像,而压缩感知成像采用优化压缩感知算法复原图像。单像素成像实验采用的光源种类繁多,既包括热光、X射线、电子、中子、单光子源等物理光源,也包括由空间光调制器和数字微镜等系统调制的人工光源。这些光源遵从不同的统计概率分布,照明物体的光场强度可看作统计独立的连续或离散随机变量,也被称为参考信号。单像素信号是所有参考信号的线性组合,根据光源的统计性质确定了参考信号与单像素信号之间的联合统计概率分布。此外,还研究了参考信号概率分布函数对关联鬼成像图像质量的影响,为单像素成像提供了物理和统计理论基础。
图像处理 单像素成像 鬼成像 密度分布函数 可见度 信噪比 激光与光电子学进展
2021, 58(10): 1011018
王超 1,2,3张学智 1,2,3江俊峰 1,2,3刘琨 1,2,3[ ... ]刘铁根 1,2,3,*
1 天津大学精密仪器与光电子工程学院, 天津 300072
2 天津大学光电信息技术教育部重点实验室, 天津 300072
3 天津大学光纤传感研究所, 天津 300072
针对水利枢纽高速气流的流速测量需求,提出了一种基于光纤法布里-珀罗(F-P)传感技术的湍流流速测量系统。该系统由风速测量探头和偏振低相干干涉解调单元组成,利用两支F-P传感器检测流场的压力和温度变化,以实现流速的计算。通过追踪单个条纹的峰位置和七步相移法,对低成本线阵CCD采集到的干涉信号进行高精度解调。在温度为20~40 ℃和压力为98~110 kPa的环境下对两支传感器进行标定,用于滞止压力测量的传感器的压力绝对误差小于0.018 kPa,用于流场温度测量的传感器的温度绝对误差小于0.08 ℃。利用该系统进行了速度为9.3~93 m/s的气流检测,流速绝对误差小于0.49 m/s。实验结果表明,该系统可以实现高速湍流的流速测量,成本低,有广泛的应用前景。
光纤光学 光纤传感器 法布里-珀罗 低相干干涉 相移干涉法 流体测量 光学学报
2020, 40(12): 1206005
Guanhua Liang 1,2,3Junfeng Jiang 1,2,3,*Kun Liu 1,2,3Shuang Wang 1,2,3[ ... ]Tiegen Liu 1,2,3,4
Author Affiliations
Abstract
1 School of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China
2 Institute of Optical Fiber Sensing of Tianjin University, Tianjin Optical Fiber Sensing Engineering Center, Tianjin 300072, China
3 Key Laboratory of Opto-electronics Information Technology (Tianjin University), Ministry of Education, Tianjin 300072, China
4 e-mail: tgliu@tju.edu.cn
A phase demodulation method for quasi-distributed acoustic sensing (DAS) systems based on a dual-identical-chirped-pulse and weak fiber Bragg gratings (WFBGs) is proposed. Compared to the use of Rayleigh backscattering light in optical fibers, the implementation of WFBGs can contribute to obtaining an optical signal with a higher signal-to-noise ratio (SNR). The dual-identical-chirped-pulse is generated by a time-delay fiber, and the sinusoidal carrier is generated by the interference between the two chirped pulses reflected by adjacent WFBGs. The phase of the sinusoidal carrier represents the dynamic strain change posed on the sensing fiber. Discrete Fourier transform is used to directly retrieve the phase information. The performance of the phase demodulation from interference signals under different sinusoidal carrier frequencies and SNRs is numerically investigated. The piezoelectric transducer is employed to emulate the sound in the experiment to verify the effectiveness of our method. It is shown that the dynamic strain can be well reconstructed at the end of a 101.64 km fiber when the signal SNR is down to 3.234 dB. Our proposed method enables the application of the long-distance sensing in quasi-DAS systems.
Photonics Research
2020, 8(7): 07001093
1 天津大学精密仪器与光电子工程学院, 天津 300072
2 光电信息技术教育部重点实验室, 天津 300072
针对现有的刀头磨损检测方法检测难度大、无法实时监测的缺点,提出一种基于光纤布拉格光栅(FBG)阵列的刀具磨损检测新方法。在实验上搭建了多路光纤光栅磨损检测系统,通过对光纤光栅的定位和波分复用能力进行分析,得到了可应用于刀头磨损检测领域的嵌入式光学传感器,将4根栅区长度为3 mm的FBG阵列等间隔分立布置,并同时进行解调。利用该方法实现了对磨损长度的在线实时监测,磨损检测误差在0.23 mm以内。
光纤光学 光纤传感 光纤布拉格光栅阵列 磨损检测 实时 光学学报
2019, 39(12): 1206003
Xiaojun Fan 1,2,3Junfeng Jiang 1,2,3,*Xuezhi Zhang 1,2,3,**Kun Liu 1,2,3[ ... ]Tiegen Liu 1,2,3
Author Affiliations
Abstract
1 School of Precision Instrument and Opto-electronics Engineering, Tianjin University, Tianjin 300072, China
2 Tianjin Optical Fiber Sensing Engineering Center, Institute of Optical Fiber Sensing of Tianjin University, Tianjin 300072, China
3 Key Laboratory of Opto-electronics Information Technology, Ministry of Education, Tianjin University, Tianjin 300072, China
A weak fiber Bragg grating (WFBG) is an ideal quasi-distributed optical fiber sensor. Special attention should be paid to the spectrum and sensing performance of the WFBG at extreme temperatures due to its poor reflection intensity. In this Letter, the temperature characteristics of the WFBG from 252.75°C to 200.94°C are experimentally investigated. Five WFBGs with reflectivity from ～0.25% to ～10% are used in the experiments. The reflectivity variations and wavelength shifts at different temperatures are studied. Experimental results show that the WFBG can survive and work at extreme temperatures, but the performance is affected significantly. The reflectivity is affected significantly by both cryogenic temperature and high temperature. The temperature responses of Bragg wavelengths in the wide temperature range are also obtained.
060.3735 Fiber Bragg gratings 060.2370 Fiber optics sensors 230.1480 Bragg reflectors Chinese Optics Letters
2019, 17(12): 120603
