Phase-resolved optical coherence tomography and optical Doppler tomography for imaging blood flow in human skin with fast scanning speed and high velocity sensitivity

We have developed a novel phase-resolved optical coherence tomography (OCT) and optical Doppler tomography (ODT) system that uses phase information derived from a Hilbert transformation to image blood flow in human skin with fast scanning speed and high velocity sensitivity. Using the phase change between sequential scans to construct flow-velocity imaging, this technique decouples spatial resolution and velocity sensitivity in flow images and increases imaging speed by more than 2 orders of magnitude without compromising spatial resolution or velocity sensitivity. The minimum flow velocity that can be detected with an axial-line scanning speed of 400 Hz and an average phase change over eight sequential scans is as low as 10 microm/s, while a spatial resolution of 10 microm is maintained. Using this technique, we present what are to our knowledge the first phase-resolved OCT/ODT images of blood flow in human skin.     

Supercontinuum light source enables in vivo optical microangiography of capillary vessels within tissue beds

This Letter reports on the use of a supercontinuum light source to achieve ultrahigh resolution and ultrahigh sensitive optical microangiography (OMAG) imaging of microcirculations within tissue beds in vivo. After passing through a specially designed optical filter with a passband of 120 nm centered on 800 nm, the light source is coupled into an optic-fiber-based OMAG system that provides a measured axial resolution of ～3 μm over a ranging distance of 2 mm. Within this ranging distance, the system gives an averaged signal-to-noise ratio of 87 dB and a sensitivity roll-off of 7 dB at an A-scan rate of 70 kHz. We demonstrate the capability of the system to visualize a detailed microvascular perfusion map, including the single red blood cells within the capillaries, by imaging a mouse ear flap in vivo.     

一种光栅型成像光谱仪光学系统设计

 成像光谱仪是一种“图谱合一”的光学遥感仪器。从光栅型成像光谱仪的使用要求出发,利用Zemax软件设计了一种光栅型成像光谱仪光学系统。其中,前置望远物镜采用反射式结构,传统的卡塞格林结构在主次镜均采用非球面时校正像差的能力依然有限,设计时采用改进后的卡塞格林结构对像差进行校正,最终设计的望远镜头传函在50 lp/mm处达到0.5,场曲控制在0.078以内,且不存在畸变。针对光谱成像系统通常采用的基于平面光栅的Czerny-Turner结构由于像差校正能力有限、成像质量较差不能满足仪器的使用要求。采用基于凸面光栅的光谱成像系统,该系统结构紧凑、可实现宽波段内像差的同时校正。最终设计的光谱成像系统光谱分辨率<5 nm,MTF在50 lp/mm时升至0.75。将前置望远物镜与光谱成像系统根据匹配原则进行组合优化后光栅型成像光谱仪系统点列图RMS半径随波长的变化均小于0.2,波长的80%的能量集中在Φ6 μm范围内,波长各视场在特征频率50 lp/mm处的光学传递函数均大于0.5。整个光学系统具有结构简单、像差校正能力强、结构尺寸较小的优点。     

小型化望远式激光共焦扫描显微内窥镜

研制了一种激光共焦扫描显微内窥镜,采用望远式显微内窥光学系统,同时实现长距离的图像中继传输、远心f-theta光学扫描和显微内窥成像功能.二维共焦扫描由双振镜实现,低噪音扫描控制信号由嵌入式系统产生.为实现便携式应用,激光共焦扫描显微内窥镜采用小型化设计方案.首先,体内的显微内窥成像光学系统,外径尺寸为8 mm,工作长度为250.3 mm,可通过标准腹腔镜手术孔进行体内显微内窥成像;其次,采用3 mm通光孔径的小尺寸平面反射镜实现体外共焦扫描,摆动频率为100 Hz,实现快速共焦扫描;最后,激光控制和荧光探测仅通过电缆和光纤与共焦扫描显微内窥镜前端连接,减小了显微内窥镜的前端尺寸和重量.通过实验验证,本系统的成像视场为φ 600 μm,光学分辨率为2.2 μm,可采用手持式或者其他方式工作,进行体内组织的共焦扫描成像,实现微创、在体的荧光显微内窥术.     

扫描型长波红外连续变焦光学系统

基于斯特林制冷式4×288元光伏型碲镉汞二维探测器, 根据红外扫描成像系统原理, 设计了一个扫描型长波红外连续变焦光学系统。根据系统指标要求对光学指标进行分解计算及光学优化设计得到系统的光学参数和外形结构图, 并对扫描光学系统的冷反射进行分析优化。该光学系统采用三次成像的结构, 由变焦望远镜组、扫描摆镜、中继镜组、成像镜组4部分组成, 包含9片透镜和2片反射镜。为了降低校正色差成本, 系统使用了硫系玻璃镜片。光学仿真结果表明:系统在耐奎斯特频率处的全视场光学传递函数大于0.35, 全视场畸变小于2%。最后, 对系统进行了成像实验验证, 结果表明:该系统可以实现30.8~154 mm范围内连续变焦, 变焦过程中目标景物清晰, 细节分辨率高, 无冷反射现象出现, 该系统具有分辨率高、热灵敏度高、像质清晰等特点。     

Terahertz single pixel imaging based on a Nipkow disk

We describe a terahertz single pixel imaging system based on a Nipkow disk. Nipkow disks have been used for fast scanning imaging systems since the first experimental television was invented in 1926. In our work, a Nipkow disk with 24 scanning lines was used to provide an axial resolution of 2 mm/pixel. We also show that by implementing a microscanning technique the axial resolution can be further improved to 0.5 mm/pixel. Imaging of several objects was demonstrated to show that this simple scanning system is promising for fast or real time terahertz imaging applications.     

基于声学扫描振镜的超声/光声双模态成像技术

超声/光声双模态成像技术因其同时兼具超声的高分辨率结构成像和光声的高对比度功能成像优势,极大地推动了光声成像技术的临床应用推广.传统超声/光声双模态成像技术多基于超声成像所用阵列探头同时收集光声信号,系统结构紧凑且无需图像配准,操作便捷.但该类设备使用阵列探头和多通道数据采集,使得其成本较高;且成像结果易受通道一致性差异影响.本文提出了一种基于声学扫描振镜的超声/光声双模态成像技术,该技术采用单个超声换能器结合一维声学扫描振镜进行快速声束扫描,实现超声/光声双模态成像,是一种小型化、低成本的双模态快速成像技术.本文开展了系列仿体和活体成像研究,实验结果表明:系统有效成像范围为15.6 mm,超声和光声成像B扫描速度分别为1.0 s^–1和0.1 s^–1 (光声成像速度主要受制于脉冲激光器重复频率).基于本文所提技术研究,有助于进一步推动超声/光声双模态成像技术的临床转化和普及;也为基于超声信号检测的多模态成像技术提供了一种低成本、小型化和快速声信号检测的参考方案.     

Near-infrared laser scanning confocal microscopy and its application in bioimaging

Near-infrared (NIR) fluorescence imaging is an important imaging technology in deep-tissue biomedical imaging and related researches, due to the low absorption and scattering of NIR excitation and/or emission in biological tissues. Laser scanning confocal microscopy (LSCM) plays a significant role in the family of fluorescence microscopy. Due to the introduction of pinhole, it can provide images with optical sectioning, high signal-to-noise ratio and better spatial resolution. In this study, in order to combine the advantages of these two techniques, we set up a fluorescence microscopic imaging system, which can be named as NIR-LSCM. The system was based on a commercially available confocal microscope, utilizing a NIR laser for excitation and a NIR sensitive detector for signal collection. In addition, NIR fluorescent nanoparticles (NPs) were prepared, and utilized for fluorescence imaging of the ear and brain of living mice based on the NIR-LSCM system. The structure of blood vessels at certain depth could be visualized clearly, because of the high-resolution and large-depth imaging capability of NIR-LSCM.     

Fourier domain optical coherence tomography using optical demultiplexers imaging at 60,000,000 lines/s

We describe high-speed Fourier domain optical coherence tomography (OCT) using optical demultiplexers (ODs) for spectral dispersion. The OD enables separation of a narrow spectral band of 14 GHz (0.11 nm) from a broadband incident light at 256 different frequencies in 25.0 GHz intervals centered at 192.2 THz (1559.8 nm). OCT imaging of 60,000,000 axial scans per second was achieved through parallel signal acquisition using 256 balanced photoreceivers to simultaneously detect all the output signals from the ODs in a Fourier domain OCT system. OCT imaging at a 16 kHz frame rate, 1100 A-lines per frame, 3 mm depth range, and 23 microm resolution was demonstrated using a resonant scanner for lateral scanning.     

CMOS detector arrays in a virtual 10-kilopixel camera for coherent terahertz real-time imaging

We demonstrate the principle applicability of antenna-coupled complementary metal oxide semiconductor (CMOS) field-effect transistor arrays as cameras for real-time coherent imaging at 591.4 GHz. By scanning a few detectors across the image plane, we synthesize a focal-plane array of 100×100 pixels with an active area of 20×20 mm2, which is applied to imaging in transmission and reflection geometries. Individual detector pixels exhibit a voltage conversion loss of 24 dB and a noise figure of 41 dB for 16 μW of the local oscillator (LO) drive. For object illumination, we use a radio-frequency (RF) source with 432 μW at 590 GHz. Coherent detection is realized by quasioptical superposition of the image and the LO beam with 247 μW. At an effective frame rate of 17 Hz, we achieve a maximum dynamic range of 30 dB in the center of the image and more than 20 dB within a disk of 18 mm diameter. The system has been used for surface reconstruction resolving a height difference in the μm range.     

高分辨率快速数字化光声CT乳腺肿瘤成像

提出了一种基于聚焦线性阵列探测器的快速光声计算机断层成像技术（光声CT）.在光声二维图像重建中,根据阵列探测器机械扫描和电子扫描相结合的组合扫描模式,提出了改进的有限场滤波反投影重建算法.一方面该算法适合多元探测器旋转扫描模式,另一方面探测器的指向性函数作为反投影的权重因子提高了系统的横向分辨率.同时,该成像系统还利用柱面声透镜实现Z轴方向上的聚焦扫描以实现三维层析成像.实验中,这套成像系统空间分辨率达到0.2mm,Z轴方向分辨率为1.5mm,扫描一幅二维图像仅需150s,得到 关键词： 光声CT 有限场滤波反投影算法 声透镜聚焦 乳腺肿瘤检测     

小型条纹管数值模拟及实验研究

针对无人机载及星载激光成像雷达系统对条纹管的小型化、高空间分辨率与大探测面积的应用需求,研制了一台具有高边缘空间分辨能力、高亮度增益的小型条纹相机.采用球面光电阴极、球面荧光屏技术提高了条纹相机的边缘空间分辨率和探测面积,有利于增大激光成像雷达的探测视场;采用狭缝型加速电极代替传统栅网电极,有利于提高条纹相机的电耐性和可靠性;设计了加载高达-15 kV工作电压的像缩小型条纹管,增大了条纹管的亮度增益,有助于增大激光雷达系统的探测距离.测试结果显示：在有效工作面积16 mm×2 mm内,条纹管静态空间分辨率高于29.3 lp/mm@MTF=5%（MTF表示调制传递函数）,亮度增益高达39.4.条纹相机光电阴极处静态空间分辨率高于15 lp/mm@CTF=11.64%（CTF表示对比度传递函数）;边缘动态空间分辨率高于9.8 lp/mm@CTF=5.51%;时间分辨率优于54.6 ps@T_screen=4.3 ns（T_screen为全屏时间）且在整个工作面积内具有较高的一致性;动态范围为345：1@54.6 ps.同时,为满足不同的景深及探测精度需求,相机设置六个扫描档位,可以实现不同扫速下的超快速目标诊断.该条纹相机在无人机载及星载激光成像雷达探测中具有潜在的实用价值.     

成像型任意反射面速度干涉仪研制

成像型任意反射面速度干涉仪是激光驱动冲击波研究的重要诊断设备,主要应用于惯性约束聚变脉冲整形实验、高压状态方程实验研究和材料特性研究.基于传统任意反射面速度干涉仪的特点,研制了一台基于神光Ⅲ原型装置的成像型任意反射面速度干涉仪,该系统可用于测量自由面速度及透明介质中的冲击波速度.给出了成像型任意反射面速度干涉仪的详细设计要点.对系统性能进行了分析及测试,结果表明时间分辨优于30 ps,物方空间分辨约为10 μm,测速范围为6～45 km/s.     

水下同步扫描三角测距成像理论建模及仿真分析

针对激光同步扫描三角测距成像系统水下应用时,考虑不同介质界面的折射效应,通过理论建模,得出水下同步扫描三角测距成像系统的空间三维坐标测量关系表达式。分析了基线距离、接收透镜焦距等系统主要参数对距离测量分辨率的影响,以及成像探测器长度对测量范围的影响。仿真结果表明:增大基线距离和接收透镜焦距,有利于提高距离测量分辨率,增加成像探测器长度,有利于增大系统测量范围,为水下同步扫描三角测距成像系统的设计提供了理论依据。     

Intraoperative spectral domain optical coherence tomography for vitreoretinal surgery

We demonstrate in vivo human retinal imaging using an intraoperative microscope-mounted optical coherence tomography system (MMOCT). Our optomechanical design adapts an Oculus Binocular Indirect Ophthalmo Microscope (BIOM3), suspended from a Leica ophthalmic surgical microscope, with spectral domain optical coherence tomography (SD-OCT) scanning and relay optics. The MMOCT enables wide-field noncontact real-time cross-sectional imaging of retinal structure, allowing for SD-OCT augmented intrasurgical microscopy for intraocular visualization. We experimentally quantify the axial and lateral resolution of the MMOCT and demonstrate fundus imaging at a 20Hz frame rate.     

Real-time phase-resolved functional optical coherence tomography by use of optical Hilbert transformation

We have developed a novel real-time phase-resolved functional optical coherence tomography system that uses optical Hilbert transformation. When we use a resonant scanner in the reference arm of the interferometer, with an axial scanning speed of 4 kHz, the frame rate of both structural and Doppler blood-flow imaging with a size of 100 by 100 pixels is 10 Hz. The system has high sensitivity and a larger dynamic range for measuring the Doppler frequency shift that is due to moving red blood cells. Real-time images of in vivo blood flow in human skin obtained with this interferometer are presented.     

太赫兹远距离快速扫描成像系统的设计

在太赫兹成像技术研究中,分辨率、成像时间和距离是非常关键的参数指标,为了推动太赫兹成像技术的实用化,特别是提高对隐藏危险物品的远距离快速预警检测能力,提出被动式远距离太赫兹快速扫描成像系统。该系统采用单个太赫兹探测器和光机扫描相结合的方式。扫描子系统中,将六面体转镜置于离轴三反镜系统的平行光路中,使扫描范围从广泛研究中采用的物空间转换到像空间有效缩小了扫描区域,缩短了成像时间。本套被动式扫描成像系统主要参数:探测器频率0.34 THz,成像距离10 m,视场1.51.5,成像分辨率3 cm,成像时间1 s。     

大量程激光位移传感器的成像系统设计

为了解决目前国内自主研发的激光位移传感器基准工作距离短和测量范围小的问题,设计了一种适用于远距离测量的大量程激光位移传感器成像光学系统。基于激光三角测量原理,结合具体使用要求计算了大量程激光位移传感器的性能指标和成像光学系统的设计参数。选择5片式透镜结构作为系统的初始结构,利用光学设计软件对大量程激光位移传感器成像光学系统进行了仿真,完成了系统优化和性能分析,实现了基准工作距离为1 000 mm、量程为±500 mm、分辨率为0.4 mm的大量程激光位移传感器成像系统设计。结果表明,在测量范围±500 mm内,系统均可以满足成像质量要求。该激光位移传感器成像系统具有工作距离远、测量量程大、结构简单的特点,可满足1 000 mm远距离处大量程范围的测量使用要求。     

共焦扫描显微成象的光学断层平面分辨率与信噪比之间的关系

在Fried的一维分辨度理论的基础上,系统地讨论了光学成象系统两维分辨率与信噪比之间的定量关系,并以反射式共焦显微成象为例,建立了实际显微成象系统分辨率的定量计算方法.所得出的结果对于选择共焦扫描显微成象系统的最佳参量及评价所设计的显微成象系统的性能具有重要的意义.     

A compact optical parametric oscillator Raman microscope for wavelength‐tunable multianalytic microanalysis

We have developed a high‐throughput microscope for wavelength‐tunable microscopic studies of materials by Raman, surface‐enhanced Raman, fluorescence, and reflectance spectroscopy. Narrow‐band excitation over a broad tuning range (410–2200 nm) is provided by a solid‐state, compact, and relatively inexpensive new class of diode‐pumped Nd:YAG optical parametric oscillator emitting approximately 1‐mJ, 10‐ns pulses at a rate up to 100 Hz. Rayleigh rejection over the tuning range is obtained with an array of angle‐tuned custom dielectric filters. Although high‐power, low duty‐cycle light sources have so far had only very limited use for tunable Raman and surface‐enhanced Raman spectroscopy, we show that undesirable nonlinear effects that arise from the high peak power of the output can be mitigated to produce good results with the proper choice of additional microscope elements. Measurements can be performed across the visible range with 20% sample‐to‐detector throughput and 10 cm⁻¹ resolution. The system is also fitted with a fiber optic imaging system to perform fluorescence and reflectance spectroscopy measurements with a spatial resolution of 5 µm. We demonstrate the instrument's analytical capabilities by recording resonance Raman and surface‐enhanced Raman emissions from a commercial lake pigment and crystal violet, respectively, colorants of interest in cultural heritage studies and forensic science. We also isolate and measure the reflectance spectrum of a commercial lake pigment and the ultraviolet fluorescence spectrum of a single fiber of cochineal‐dyed silk. The tunability, flexibility, compactness, and spatial resolution of the device provide novel capability for multianalytic materials research in fields such as forensic science and cultural heritage studies. Copyright © 2012 John Wiley & Sons, Ltd.