Author Affiliations
Abstract
1 MOE Key Laboratory of Advanced Micro-structured Materials, School of Physics Sciences and Engineering, Tongji University, Shanghai 200092, China
2 School of Space Science and Physics, Shandong University, Weihai 264209, China
3 State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
4 Department of Electrical Engineering, Tongji University, Shanghai 201804, China
5 e-mail: yufeiwang@semi.ac.cn
6 e-mail: jiang-haitao@tongji.edu.cn
7 e-mail: dgqql@sdu.edu.cn
8 e-mail: yongsun@tongji.edu.cn
Recently, the concepts of parity–time (PT) symmetry and band topology have inspired many novel ideas for light manipulation in their respective directions. Here we propose and demonstrate a perfect light absorber with a PT phase transition via coupled topological interface states (TISs), which combines the two concepts in a one-dimensional photonic crystal heterostructure. By fine tuning the coupling between TISs, the PT phase transition is revealed by the evolution of absorption spectra in both ideal and non-ideal PT symmetry cases. Especially, in the ideal case, a perfect light absorber at an exceptional point with unidirectional invisibility is numerically obtained. In the non-ideal case, a perfect light absorber in a broken phase is experimentally realized, which verifies the possibility of tailoring non-Hermiticity by engineering the coupling. Our work paves the way for novel effects and functional devices from the exceptional point of coupled TISs, such as a unidirectional light absorber and exceptional-point sensor.
Photonics Research
2023, 11(4): 517
浙江大学光电科学与工程学院, 浙江 杭州 310027
显微镜倍率越大,视野越小,通常需要通过图像拼接得到视野范围大且分辨率高的切片图像。而显微图像拼接时,由于特征丰富、信息量大且包含大量相似区域,导致拼接时间过长,配准准确率低。为此,提出了一种针对显微图像的拼接算法,可以快速进行配准和融合得到拼接图像。首先通过模板匹配进行初始运动估计,然后用光流法做进一步匹配,得到匹配点对后通过相似性和位置约束剔除误匹配点,进一步提高配准精度。实验结果表明,所提方法可以在保持实时性的同时有效提高配准精度。
图像处理 图像配准 光流法 模板匹配 位置约束 激光与光电子学进展
2021, 58(24): 2410001
浙江大学光电科学与工程学院, 浙江 杭州 310027
目标计数作为一项基础的技术,在许多领域都有广泛的应用,如人群计数、细胞计数、车辆计数等。随着互联网时代的信息爆炸,视频数据呈指数级增长,如何快速、准确地获得目标的数量是用户普遍关心的主要问题之一。得益于计算机视觉技术的快速发展,基于传统机器学习的计数方法正逐步向基于深度学习的方法转变,并在计数的准确性上取得了实质性的进展。介绍了目标计数的研究背景和应用领域,根据模型任务分类,归纳了三类常用的计数模型框架,并从不同的角度分别介绍了近10年来基于计算机视觉技术的模型方法。然后介绍了在人群计数、细胞计数和车辆计数领域中常用的几种公开数据集,并横向比较了各个模型之间的性能。最后总结了现阶段的目标计数模型还存在的不足,并对未来的研究方向进行了展望。
图像处理 目标计数 神经网络 机器学习 密度图 激光与光电子学进展
2021, 58(14): 1400002
浙江大学光电科学与工程学院， 浙江 杭州 310027
深空图像配准是深空图像应用的首要环节。针对目前基于三角形相似性的算法效率低下以及基于星点描述的算法难以应对复杂多变的深空成像环境等问题，提出了一种改进型高效三角形相似法并将其应用到深空图像配准中。首先统计分析了提取星点单像素强度和大小的直方图分布，并将星点划分为稳定星和普通星；然后，将稳定星和普通星分别同最近的两颗稳定星构建三角形；最后，通过引入相似度改进了三角形匹配中的权重矩阵，并提出了衡量三角形相似度的阈值自适应计算方法。实验结果表明，该方法在保证匹配精度的同时极大地提高了深空图像配准的效率，降低了系统资源占用率。
图像处理 图像配准 三角形相似性 深空图像 星点匹配
Author Affiliations
Abstract
1 State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310027, China
2 Computer Science Department, University of Southern California, 941 Bloom Walk, Los Angeles, CA 90089, USA
Image registration is an old topic but has a new application in deep-sky imaging fields named live stacking. In this Letter, we propose a live stacking algorithm based on star detection, description, and matching. A thresholding method based on Otsu and centralization is proposed to implement star detection. Then, a translation and rotation invariant descriptor is proposed to provide accurate feature matching. Extensive experiments illustrate that our proposed method is feasible in deep-sky image live stacking.
150.1135 Algorithms 100.4994 Pattern recognition, image transforms 350.1260 Astronomical optics Chinese Optics Letters
2016, 14(12): 121501
浙江大学 光电信息工程学系,浙江 杭州310027
从反射积分球模型入手,建立待测样品反射率同积分球及光源相关参数的关系,分析非中性对反射积分球模型的影响。将反射率验证转换为光谱辐射出射度验证,通过实际测量对比,验证了积分球出口处的光谱辐射出射度。结果表明:400～700 nm波段,反射积分球模型与实验测量值基本一致,非中性的影响较小;700～1 000 nm波段,非中性模型较普通模型相对误差较小。另外,500～850 nm波段非中性模型相对误差优于5%。
积分球模型 反射率 辐射定标 非中性 integrating sphere model reflectivity radiation calibration non-neutral
