1 重庆大学光电技术及系统教育部重点实验室ICT研究中心，重庆 400044
2 重庆大学工业CT无损检测教育部工程研究中心，重庆 400044
3 中国工程物理研究院化工材料研究所，四川 绵阳 621900
4 中国工程物理研究院激光聚变研究中心高温高密度等离子体物理实验室，四川 绵阳 621900
超快激光X射线单发照相技术具有高时空分辨能力，是观测高速运动物体形态参数如内部结构、平面性等的重要手段。但由于激光X射线脉宽在皮秒或飞秒量级、X射线能谱宽、成像环境复杂等原因，导致X射线图像背景干扰噪声大、对比度低，物体形态结构准确识别和测量难度大。在传统对比度限制直方图均衡化（CLAHE）图像增强算法的基础上，提出了一种多尺度融合的改进直方图均衡化（IHEMF）算法。该算法增加自适应裁剪阈值以适应每个区域特征，并利用亮度和梯度幅值信息将增强后图像与原始图像全局融合，最后对融合后图像去噪得到最终图像。该算法既能提高感兴趣区域的对比度噪声比（CNR），又具有很好的保边界特征的能力。对高速飞片的静态、动态、终态等典型状态下X射线图像进行处理，CNR分别提升50.97%、90.43%和96.84%。实验结果表明所提算法在噪声抑制和结构保真方面优于其他算法，可为准确解读高速运动物体形态表征参数信息提供重要技术支撑。
超快激光 X射线单发照相 图像增强 多尺度融合 直方图均衡化 中国激光
2023, 50(22): 2209001
光子学报
2022, 51(11): 1130001
Author Affiliations
Abstract
1 Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
2 Key Laboratory for Special Functional Materials of the Ministry of Education, Henan University, Kaifeng 475004, China
3 School of Information Engineering, Xinyang Agriculture and Forestry University, Xinyang 464000, China
4 Department of Physics, South University of Science and Technology, Shenzhen 518055, China
Controlling quantum dots’ emission, nanostructure, and energy level alignment to achieve stable and efficient blue emission is of great significance for electroluminescence devices but remains a challenge. Here, a series of blue ZnCdSeS/ZnS quantum dots was optimized in preparation by taming their nucleation and growth kinetics. Controlling anion precursor reactive properties to modulate quantum dots’ nucleation and growth tailors their alloy core and continuous gradient energy band nanostructure. These results not only elevate the thermal stability of blue quantum dots but also further enhance the injection/transportation of carriers and improve the radiative recombination efficiency in the device. The blue ZnCdSeS/ZnS quantum dots applied in light-emitting devices show superior performance, including maximum current efficiency and external quantum efficiency of, respectively, 8.2 cd/A and 15.8% for blue, 2.6 cd/A and 10.0% for blue-violet, and 10.9 cd/A and 13.4% for sky-blue devices. The blue and sky-blue devices exhibit lifetimes of more than 10,000 h. The proposed methodology for tailoring quantum dots is expected to pave new guidelines for further facilitating visible optoelectronic device exploration.
Photonics Research
2022, 10(10): 2359
1 重庆大学光电技术及系统教育部重点实验室, 重庆 400044
2 重庆大学工业CT无损检测教育部工程研究中心, 重庆 400044
常规显微计算机断层成像(CT)存在空间分辨率越高CT扫描视场越小的矛盾。近年来提出的基于电子束偏转扫描阵列微焦点X射线源的大视场显微CT(EBMCT),不仅保持了高空间分辨率的优点,也大幅扩大了CT扫描视场,增大了可检样品的尺寸。但EBMCT特殊的多焦点阵列扫描方式,导致其投影数据既存在截断问题也存在冗余问题。目前EBMCT一般采用对投影数据要求不高的迭代图像重建算法。然而,阵列焦点的投影数据量庞大,迭代算法的计算消耗大、重建时间长,难以满足EBMCT快速CT扫描检测需求。提出了一种平滑加权多源滤波反投影(MSFBP)算法。仿真和实验结果表明,算法很好地消除了投影数据冗余带来的伪影,并较好地抑制了截断伪影;均方根误差、峰值信噪比、结构相似性、空间分辨率等重建图像质量指标均优于常规重排等传统图像重建算法。在计算机硬件、图像矩阵等相同的条件下,所提算法的重建速度比联合代数迭代重建算法快3.3倍以上,为EBMCT系统在快速、大视场CT检测应用方面提供了良好的基础。
光学学报
2022, 42(11): 1134023
无锡职业技术学院机械技术学院，江苏 无锡 214121
为改善钛合金（TC4）零部件硬度低、耐磨性差等缺陷，利用激光熔覆技术在TC4表面制备碳化硼/钴基合金（B4C/Cobalt-based）复合涂层。通过有限元法对复合涂层的温度场进行数值模拟，结合复合涂层的表面形貌和显微硬度分析，研究激光功率对单道激光熔覆B4C/Cobalt-based复合涂层的影响。结果表明：随着激光功率的升高，熔池峰值温度升高，热影响区增大，熔池深度增加，宽度几乎无变化；当激光功率为1 600 W时，复合涂层的显微硬度达到最高值，为618.7 HV（2 N加载力），相较于TC4基底提升了79.2%，结合仿真和试验结果揭示了B4C的增强机理。
激光熔覆 数值模拟 碳化硼/钴基合金 显微硬度 laser cladding numerical simulation B4C /Cobalt-based alloy micro-hardness
Author Affiliations
Abstract
Department of Bioengineering Joint Graduate Program between University of Texas at Arlington and University of Texas Southwestern Medical Center University of Texas at Arlington, TX 76019, USA
Ultrasound-guided biopsy procedure for prostate cancer diagnosis, which is the current gold standard, involves quasi-random sampling of prostate tissue without any functional guidance. In this study, we discuss the possibility to augment the detection of prostate cancer using a dual-modality optical approach, which can be coupled with the current needle biopsy setup. Two techniques are light reflectance spectroscopy (LRS) that uses a broadband light source and a CCD array spectrometer, and auto-fluorescence lifetime measurement (AFLM) that uses a custom- designed, time-correlated single photon counting (TCSPC) system. Both LRS and AFLM were employed sequentially in this study to measure cancer tissue along with control tissue on a rat prostate tumor model. At an excitation wavelength of 447 nm, we investigated auto-fluorescence decay curves at the emission wavelengths of 532, 562, 632 and 684 nm for in vivo and ex vivo AFLM. These results show that auto-fluorescence lifetimes at all measured emission wavelengths differ between control and cancerous tissues with 100% specificity and sensitivity. Moreover, absolute values of hemoglobin derivatives and scattering coefficient were quantified using in vivo LRS. This part of study also demonstrates that light scattering and absorption are significantly different between the control and cancerous tissue. Overall, the study demonstrates that both LRS and AFLM may provide several intrinsic biomarkers for in vivo detection of prostate cancer.
Prostate cancer light reflectance spectroscopy auto-fluorescence lifetime Journal of Innovative Optical Health Sciences
2011, 4(3): 269
解放军理工大学气象学院, 江苏 南京 211101
搜集整理了大气粒子观测资料，运用米氏理论，从求解Mueller矩阵入手，计算并分析了可见光和红外波段大气体散射的偏振度特性。结果表明，大气体散射总体上为正偏振，前向散射不改变入射光的偏振状态，后向散射存在轻微的负偏振；大气线偏振度随散射角分布比较平滑，随着尺度参数的减小趋于瑞利散射的情况；散射尺度参数和粒子复折射指数是大气线偏振度的决定因子；在可见光与近红外波段，雾线偏振度随波长变化较小，随散射角呈“多峰”形式分布，在120°,140°和180°达到极大值；在红外波段，气溶胶线偏振度随波长变化较小，随散射角呈“单峰”分布形式，极大值出现在80°~140°之间。
大气光学 可见光 红外 气溶胶 雾 散射 线偏振度
