Author Affiliations
Abstract
1 Sun Yat-Sen University, State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Guangzhou, China
2 Sun Yat-Sen University, Guangdong Provincial Key Laboratory of Quantum Metrology and Sensing, School of Physics and Astronomy, Zhuhai, China
3 Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai, China
Scattered light imaging through complex turbid media has significant applications in biomedical and optical research. For the past decade, various approaches have been proposed for rapidly reconstructing full-color, depth-extended images by introducing point spread functions (PSFs). However, because most of these methods consider memory effects (MEs), the PSFs have angular shift invariance over certain ranges of angles. This assumption is valid for only thin turbid media and hinders broader applications of these technologies in thick media. Furthermore, the time-variant characteristics of scattering media determine that the PSF acquisition and image reconstruction times must be less than the speckle decorrelation time, which is usually difficult to achieve. We demonstrate that image reconstruction methods can be applied to time-variant thick turbid media. Using the time-variant characteristics, the PSFs in dynamic turbid media within certain time intervals are recorded, and ergodic scattering regimes are achieved and combined as ensemble point spread functions (ePSFs). The ePSF traverses shift-invariant regions in the turbid media and retrieves objects beyond the ME. Furthermore, our theory and experimental results verify that our approach is applicable to thick turbid media with thickness of 1 cm at visible incident wavelengths.
scattered light imaging memory effect thick turbid media image reconstruction Advanced Photonics Nexus
2023, 2(2): 026010
Author Affiliations
Abstract
1 Jiangsu Provincial Engineering Laboratory for Laser Additive Manufacturing of High-Performance Metallic Components, College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Yudao Street 29, Nanjing 210016, People’s Republic of China
2 Institute of Machinery Manufacturing Technology, China Academy of Engineering Physics, Mianyang, Sichuan 621000, People’s Republic of China
Laser additive manufacturing (AM) of lattice structures with light weight, excellent impact resistance, and energy absorption performance is receiving considerable attention in aerospace, transportation, and mechanical equipment application fields. In this study, we designed four gradient lattice structures (GLSs) using the topology optimization method, including the unidirectional GLS, the bi-directional increasing GLS, the bi-directional decreasing GLS and the none-GLS. All GLSs were manufactureed by laser powder bed fusion (LPBF). The uniaxial compression tests and finite element analysis were conducted to investigate the influence of gradient distribution features on deformation modes and energy absorption performance of GLSs. The results showed that, compared with the 45° shear fracture characteristic of the none-GLS, the unidirectional GLS, the bi-directional increasing GLS and the bi-directional decreasing GLS had the characteristics of the layer-by-layer fracture, showing considerably improved energy absorption capacity. The bi-directional increasing GLS showed a unique combination of shear fracture and layer-by-layer fracture, having the optimal energy absorption performance with energy absorption and specific energy absorption of 235.6 J and 9.5 J g-1 at 0.5 strain, respectively. Combined with the shape memory effect of NiTi alloy, multiple compression-heat recovery experiments were carried out to verify the shape memory function of LPBF-processed NiTi GLSs. These findings have potential value for the future design of GLSs and the realization of shape memory function of NiTi components through laser AM.
additive manufacturing laser powder bed fusion gradient lattice structures deformation behavior shape memory effect International Journal of Extreme Manufacturing
2022, 4(4): 045002
红外与激光工程
2022, 51(8): 20220299
1 西安电子科技大学 光电工程学院 西安市计算成像重点实验室,陕西 西安 710071
2 西安电子科技大学 杭州研究院 先进光电成像与器件实验室,浙江 杭州 311200
散射成像技术因具备透过生物组织等散射介质后清晰成像的能力而受到广泛关注。近年来,基于散斑自相关的成像方法以其非接触、无需先验信息且能够单帧成像的特点得到迅速发展。然而,散斑自相关成像受光学记忆效应的限制。当多个目标之间的距离在记忆效应范围之外时,基于散斑自相关的成像方法会导致目标自相关信息在相关域发生混叠,导致成像严重退化。文中在光学记忆效应及散斑自相关成像基本原理的基础上,首先介绍了基于散斑自相关和与散斑相关成像有关的其他散射成像技术。接着介绍了拓展光学记忆效应的主要技术及相关应用。最后总结了基于散斑相关的宽视场成像技术目前存在的问题,并对未来的发展应用进行了展望。
散射成像 宽视场 散斑相关 光学记忆效应 scatter imaging extended field of view speckle correlation optical memory effect 红外与激光工程
2022, 51(8): 20220322
1 南京航空航天大学材料科学与技术学院,江苏 南京 210016
2 江苏省高性能金属构件激光增材制造工程实验室,江苏 南京 210016
3 中国工程物理研究院机械制造工艺研究所,四川 绵阳 621999
为提升点阵结构的轻量化水平及变形能力,研究了NiTi空心杆点阵结构设计及激光增材制造。通过改变支杆内径,设计了质量系数为100%、93%、75%和50%的四种体心四方空心杆点阵结构,并利用激光粉末床熔融技术成形了对应的NiTi形状记忆合金构件。研究了空心杆点阵结构的质量系数对构件成形质量和显微组织的影响规律,采用有限元模拟法和单轴压缩实验分析了质量系数对结构压缩性能的影响规律,并通过循环压缩-热回复实验揭示了质量系数对NiTi点阵结构形状记忆效应的影响机制。研究表明:激光粉末床熔融技术制备的点阵结构成形质量好,但仍存在由凝固收缩、粘粉及台阶效应引起的尺寸偏差;质量系数为100%的点阵结构的承载能力最好,第一最大压缩载荷可达191.73 kN,对应的变形率为0.22;当质量系数降至75%时,第一最大压缩载荷为89.80 kN,构件承载能力下降53.16%,但压缩变形能力并未减弱,变形率仍可达0.21,且质量系数为75%的点阵结构的形状记忆效应最佳,在第一个压缩循环中回复率可达98.92%。
激光技术 激光粉末床熔融 NiTi合金 体心四方中空点阵结构 压缩性能 形状记忆效应 中国激光
2022, 49(14): 1402303
新疆师范大学物理与电子工程学院,新疆 乌鲁木齐 830054
由于构成一个开放量子系统周围环境的热库里总是同时含有玻色子和费米子,用混杂库而不是单一的玻色库或费米库来描述系统的热库是比较符合实际的。利用非马尔可夫量子态扩散方法,研究了同时耦合于非马尔可夫玻色库与费米库的海森伯XYZ自旋链模型的量子纠缠和量子稠密编码信道容量的动力学演化特性,并与单一非马尔可夫库中的情况进行比较。数值模拟结果显示,与单一非马尔可夫库相比,与一个混杂非马尔可夫库耦合的海森伯自旋链模型显示出更高的纠缠度、更优的量子稠密编码以及更长的弛豫时间。这说明在提高量子纠缠、优化量子稠密编码方面,混杂非马尔可夫库比单一非马尔可夫库更有优势。
量子光学 混杂非马尔可夫库 环境记忆效应 量子纠缠 量子稠密编码 量子态扩散方法 激光与光电子学进展
2022, 59(5): 0527002
1 福州大学物理与信息工程学院, 福建 福州 350108
2 福州大学机械工程及自动化学院, 福建 福州 350108
光在透过散射介质后发生散射现象,在成像系统焦平面形成无序的随机散斑图像,因此人们无法直接观测到隐藏在散射介质后的目标的图像信息与光谱信息。利用基于光学记忆效应的散斑相关成像技术,可以实现透过散射介质的目标重建,但当前研究主要针对单波段照明条件下的图像信息恢复,而目标的光谱信息在成像过程中易丢失。提出采用快照式微滤光片阵列多光谱探测器进行多光谱散射成像的方案,通过实验得到宽谱氙灯光源照明条件下的穿透散射介质成像结果。提出了基于光学记忆效应的穿透散射介质目标多光谱信息重构方法,实现了对隐藏在散射介质之后的目标多光谱信息的探测成像。针对多光谱探测器所造成的成像质量差的问题,提出了利用自相关预处理方法提升穿透散射介质多光谱成像质量的方法。
成像系统 散斑相关成像 快照式多光谱探测器 光学记忆效应 散射介质
强激光与粒子束
2021, 33(6): 065002
新疆师范大学物理与电子工程学院物理系,新疆 乌鲁木齐 830054
应用非马尔可夫量子态扩散方法探究了环境记忆效应、Dzyaloshinskii-Moriya相互作用及磁场均匀程度对海森堡XXZ自旋链的量子纠缠的影响。研究发现:环境记忆效应取值越小,环境记忆时间越长,环境的非马尔可夫性越强,量子纠缠存活的时间越长。另外还发现可以通过调控Dzyaloshinskii-Moriya相互作用和磁场的均匀程度来操控系统的量子纠缠,使系统保持较好的纠缠特性。
量子光学 非马尔可夫量子态扩散方法 环境记忆效应 Dzyaloshinskii-Moriya相互作用 磁场均匀程度 量子纠缠 激光与光电子学进展
2021, 58(7): 0727003
1 华南理工大学机械与汽车工程学院, 广东 广州 510641
2 武汉大学动力与机械学院, 湖北 武汉 430072
镍钛合金是一种常见的智能材料,具有优良的形状记忆效应,在航空航天、医学和电子等领域具有广泛应用。激光选区熔化技术能够突破传统制造工艺的局限,成形出形状复杂且性能优异的镍钛合金构件,使构件的形状、性能和功能在时间和空间维度上实现可控变化,是“4D打印”的研究热点方向之一。本文简要介绍了激光选区熔化成形镍钛合金的国内外研究进展与技术现状,分析了成形工艺、热处理工艺等对镍钛合金成形件相变温度以及形状记忆效应和超弹性两大性能的影响,总结了激光选区熔化成形镍钛合金较为适宜的工艺参数,并对SLM成形镍钛合金的未来发展进行了展望,为镍钛合金激光选区熔化“4D打印”提供参考。
激光技术 镍钛合金 激光选区熔化 相变温度 超弹性 形状记忆效应 中国激光
2020, 47(12): 1202005