1 湘潭大学自动化与电子信息学院，湖南 湘潭 411105
2 湖南华菱湘潭钢铁有限公司，湖南 湘潭 411105
针对传统方式检测钢板表面缺陷存在检测精度低、检测速度慢的问题，提出一种改进YOLOv5s算法。首先，使用基于交并比（IoU）度量距离的K-means算法对钢铁数据集进行重新聚类，获得多组锚框，通过遗传算法对其进行变异运算，得到与全体标注框更匹配的多组锚框；其次，在Mosaic数据增强上融合MixUp，抑制过拟合，提升模型的泛化能力；然后，对网络结构进行改进，融入注意力模块，进一步提高了网络的特征提取能力；最后，针对难识别样本，在损失函数中融入Focal loss，提高网络的收敛速度与检测精度。实验结果表明，改进后的YOLOv5s算法在测试集上的平均精度均值（mAP）可达78.4%，比原始的YOLOv5s算法提高了3.0个百分点，速度上与原始YOLOv5s基本持平。所提算法在保持高检测速度的基础上，检测性能也优于DDN、Faster R-CNN和YOLOv3。
YOLOv5s 钢板表面缺陷检测 注意力机制 Focal loss 激光与光电子学进展
2023, 60(4): 0415009
Author Affiliations
Abstract
State Key Laboratory of High Performance and Complex Manufacturing, College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China
In this study, an effective method is proposed for controlling a titanium foil surface’s wettability. A microholes array series is fabricated on the surface of titanium foil by a femtosecond laser under different laser energy and pulse number. The changes of the titanium surface’s morphology are characterized. When placed in a darkroom with high-temperature treatment and immersed in alcohol under UV irradiation, respectively, the femtosecond laser treated surfaces display switchable wettability. It is demonstrated that the changing between Ti-OH and Ti-O prompts the transformation between superhydrophilic and superhydrophobic. Compared with existing reports, the switchable wetting cycle is shortened to 1.5 h. The functional surfaces with switchable wettability have potential applications in oil–water separation and water mist collection.
femtosecond laser titanium foil microholes array switchable wettability Chinese Optics Letters
2021, 19(8): 082201
中南大学机电工程学院高性能复杂制造国家重点实验室, 湖南 长沙 410083
随着功能性微结构的制造品质要求不断推向新的极端,超快激光微纳制造迎来了新的挑战,如更高的加工效率、跨尺度加工、选择性加工及可控性加工等。因传统超快激光高斯光束的空间和时间能量分布在加工中的局限性,以单点聚焦扫描为主的加工方法难以满足新的制造精度、效率和跨尺度加工要求。基于此,研究者将目光聚焦到超快激光光束整形的制造方法上。本文从传统超快激光光束的特点及其加工局限性角度出发,分空域光束整形、时域光束整形和时空域协同光束整形,介绍了超快激光光束整形技术的基本原理和主要实现途径;阐述了这些技术在功能性微结构制造方面的典型应用和研究进展;最后,总结和讨论了超快激光光束整形技术应用于功能性微结构制造中存在的问题和发展前景。
激光光学 超快激光 光束整形 功能性微结构 高效制造
暨南大学信息科学技术学院电子工程系, 广东 广州 510632
傅里叶叠层显微成像(FPM)是一种能够重建宽视场和高分辨率图像的新型成像技术。传统的FPM重建算法计算成本高,重建高质量的图像需要较大的图像采集量,这些缺点使得传统重建算法的成像性能和效率较低。因此,提出一种基于深度学习的傅里叶叠层显微成像的神经网络模型,对图像进行低分辨率到高分辨率的端到端映射,有效提高成像性能和效率。首先,借助菱形采样方法进行图像采集,加速低分辨图片采集过程。其次,结合残差结构、密集连接以及通道注意力机制等模块,拓展网络深度、挖掘有用特征,增强网络模型的表达能力和泛化能力。然后,使用子像素卷积进行高效地上采样,恢复高清图像。最后,采用主观和客观的评价方法对重建结果进行评估。结果显示,本文提出的网络模型对比传统重建算法重构效果更优,且降低了计算复杂度,平均重建时间更短。同时,在保证图像重建效果不变的情况下,低分辨率图像的采集数量比传统算法减少了约一半。
成像系统 计算成像 深度学习 傅里叶叠层显微 密集连接 通道注意力 激光与光电子学进展
2020, 57(22): 221106
Author Affiliations
Abstract
State Key Laboratory of High Performance and Complex Manufacturing, College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China
In this study, we propose an effective method for the fabrication of annulus micro-/nanostructures by a femtosecond laser doughnut beam. Compared with the traditional Bessel annulus beam shaping system, this method greatly compresses the light propagation path. It is theoretically and experimentally demonstrated that the obtained axial section of the peak envelope in the processing area is two waists of the isosceles triangle. By moving the relative position of the sample, annulus microstructures with different diameters on copper sheet could be fabricated. In addition, laser induced periodic surface structures with controllable direction are fabricated by this optical system.
femtosecond laser pulse shaping doughnut beam laser induced periodic surface structures Chinese Optics Letters
2020, 18(1): 013101
Author Affiliations
Abstract
1 Hunan Key Laboratory of Super Microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha 410083, China
2 The State Key Laboratory of High Performance Complex Manufacturing, College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China
We evaluate the effects of the holes geometry drilled by a femtosecond laser on a stainless alloy with various defocused irradiation time, which ranges from 0 min to 1 h. The laser ablation efficiency is increased by a factor of 3 when the irradiation time is elevated from 0 to 30 min. Also, the morphology of the hole is observed by a scanning electron microscope, where the result indicates that the defocused irradiation time has a significant influence on the morphology changes. The reason for such changes is discussed based on the pretreatment effect and the confined plasma plume. As an application example, the microchannel is fabricated by a femtosecond laser combined with the defocused irradiation to demonstrate the advantage of the proposed method in fabricating functional structures.
140.0140 Lasers and laser optics Chinese Optics Letters
2018, 16(1): 011401
Author Affiliations
Abstract
State Key Laboratory of High Performance and Complex Manufacturing, Central South University, Changsha 410083, China
A simple technique is proposed for highly-efficient plane processing fully based on femtosecond laser beam shaping. The laser intensity distribution is transformed from a Gaussian to a donut shape. As the donut-shaped focus seems like a flat top from the side view, a plane with a high level of flatness is obtained directly by scanning once. By applying it to polishing experiments, the surface roughness can be improved significantly. The influence of scanning speed, laser pulse energy, and scanning times on the roughness is also discussed. Moreover, the scanning width can be flexibly controlled in a wide range.
140.7090 Ultrafast lasers 140.3300 Laser beam shaping Chinese Optics Letters
2018, 16(3): 031401
Author Affiliations
Abstract
The State Key Laboratory of High Performance Complex Manufacturing, College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China
A fused silica glass micro-channel can be formed by chemical etching after femtosecond laser irradiation, and the successful etching probability is only 48%. In order to improve the micro-channel fabrication success probability, the method of processing a high-temperature lattice by a femtosecond laser pulse train is provided. With the same pulse energy and scanning speed, the success probability can be increased to 98% by optimizing pulse delay. The enhancement is mainly caused by the nanostructure, which changes from a periodic slabs structure to some intensive and loose pore structures. In this Letter, the optimum pulse energy distribution ratio to the etching is also investigated.
140.0140 Lasers and laser optics 230.7380 Waveguides, channeled Chinese Optics Letters
2017, 15(7): 071403
1 中南大学 高性能复杂制造国家重点实验室, 湖南 长沙 410083
2 罗彻斯特大学光学研究所, 纽约 14627
与传统传感器相比, 全光纤马赫泽德尔干涉仪(MZI)传感器, 具有结构简单、分辨率高、稳定性好等优点, 在石油化工、健康监测、生物化学等领域有广泛应用。介绍了MZI全光纤传感器的传感机理,对比了其他的加工方法, 如电弧放电、加热拉伸、CO2激光诱导微变形等的优缺点, 详细介绍了飞秒激光加工得到的MZI传感器的结构形式、折射率和温度等传感性能。重点阐述了飞秒激光加工MZI的研究现状和优点, 并对运用飞秒激光方法加工的MZI进行了总结和展望。
飞秒激光 全光纤MZI传感器 传感特性 Femtosecond laser All fiber MZI sensors Sensing performances
Author Affiliations
Abstract
1 State Key Laboratory of High Performance and Complex Manufacturing, Central South University, Changsha 410083, China
2 Institute of Optics, University of Rochester, Rochester, NY 14627, USA
Resonant effect is found in femtosecond laser ablating Pr–Nd glass. When processed with resonant wavelength of 807 nm, resonant ablation efficiency (RAE) with a single pulse can be improved by 45.22%. Furthermore, RAE closely relates to laser intensity. For resonant ablation, RAE is increased significantly when laser intensity <0.556×1014 W/cm2 at which multiphoton ionization dominates, while it fades away when laser intensity >0.556×1014 W/cm2 at which tunnel ionization dominates. Besides, it is also found that the ablation depth increases along with the wavelength rise when multiphoton ionization dominates, while the change rule is inversed when tunnel ionization dominates.
140.7090 Ultrafast lasers 160.5690 Rare-earth-doped materials 220.4000 Microstructure fabrication 320.7110 Ultrafast nonlinear optics Chinese Optics Letters
2015, 13(5): 051403
