Light absorption distribution of uterine tissue filled with strong scattering medium irradiated by diffused light source

Determining the light absorption distribution (LAD) of uterine tissue helps the detection of endometrial carcinoma. In this work, a 3-dimensional optical model of the human uterus is proposed and examined. The model is filled with strong scattering medium (undiluted raw and homogenized milk, URHM) or air at 630 nm and 800 nm wavelengths. Monte Carlo simulations are used to find the absorption profiles of photons by transcervical laser illumination, with a cylindrically diffused light source (CDLS) or spherically diffused light source (SDLS). The results show that 800 nm is a good laser wavelength value for the detection of endometrial carcinoma by photoacoustic imaging (PAI). At the same time, the shape of the light source becomes less important in a relatively large cavity. The impacts of different scattering coefficients of CDLS on the irradiated area are demonstrated. Strong scattering medium is helpful to the illumination of the uterus cavity.     

Hybrid small animal imaging system combining magnetic resonance imaging with fluorescence tomography using single photon avalanche diode detectors

The high sensitivity of fluorescence imaging enables the detection of molecular processes in living organisms. However, diffuse light propagation in tissue prevents accurate recovery of tomographic information on fluorophore distribution for structures embedded deeper than 0.5 mm. Combining optical with magnetic resonance imaging (MRI) provides an accurate anatomical reference for fluorescence imaging data and thereby enables the correlation of molecular with high quality structural/functional information. We describe an integrated system for small animal imaging incorporating a noncontact fluorescence molecular tomography (FMT) system into an MRI detector. By adopting a free laser beam design geometrical constraints imposed by the use of optical fibers could be avoided allowing for flexible fluorescence excitation schemes. Photon detection based on a single-photon avalanche diode array enabled simultaneous FMT/MRI measurements without interference between modalities. In vitro characterization revealed good spatial accuracy of FMT data and accurate quantification of dye concentrations. Feasibility of FMT/MRI was demonstrated in vivo by simultaneous assessment of protease activity and tumor morphology in murine colon cancer xenografts.     

Ultrasonic Duplex Echo-Doppler Scanner

Ultrasonic B-mode displays are produced by a new diagnostic scanner that yields dynamic Doppler information from blood flow in addition to both static and dynamic echo information from stationary and more slowly moving tissues. The effect is produced by combining the flow imaging capability of a multigate pulse-Doppler flow detector with a fast rotational pulse-echo B-mode scanner. The duplex system was designed for performing ultrasonic echo-Doppler arteriography where the location and geometry of the interface between occlusive atherosclerotic tissue and blood is of prime concern. Initial results on normal arteries in vivo are illustrated. Spatial alignment of echo and Doppler images is obtained by using the same transducer and scanning mechanism for both. However, clinical trials on patients with verified occlusive arterial disease indicated a two-transducer system would be more desirable. It is concluded that superposition of images of both tissue and blood decreases the uncertainties inherent in the display of either image alone.     

Quantifying spatial localization of optical mapping using Monte Carlo simulations

Optical mapping techniques used to study spatial distributions of cardiac activity can be divided into two categories. 1) Broad-field excitation method, in which hearts stained with voltage or calcium sensitive dyes are illuminated with broad-field excitation light and fluorescence is collected by image or photodiode arrays. 2) Laser scanning method, in which illumination uses a scanning laser and fluorescence is collected with a photomultiplier tube. The spatial localization of the fluorescence signal for these two methods is unknown and may depend upon light absorption and scattering at both excitation and emission wavelengths. We measured the absorption coefficients (micro a), scattering coefficients (micro s), and scattering anisotropy coefficients (g) at representative excitation and emission wavelengths in rabbit heart tissue stained with di-4-ANEPPS or co-stained with both Rh237 and Oregon Green 488 BAPTA 1. Monte Carlo models were then used to simulate absorption and scattering of excitation light and fluorescence emission light for both broad-field and laser methods in three-dimensional tissue. Contributions of local emissions throughout the tissue to fluorescence collected from the tissue surface were determined for both methods. Our results show that spatial localization depends on the light absorption and scattering in tissue and on the optical mapping method that is used. A tissue region larger than the laser beam or collecting area of the array element contributes to the optical recordings.     

Tethered capsule endoscopy, a low-cost and high-performance alternative technology for the screening of esophageal cancer and Barrett's esophagus

Esophageal cancer is currently the fastest growing cancer in the United States. To help combat the recent rise in morbidity, our laboratory has developed a low-cost tethered capsule endoscope system (TCE) aimed at improving early detection of esophageal cancer. The TCE contains a resonant fiberoptic laser scanner (1.6 mm O.D.) which fits into 6.4-mm easy-to-swallow capsule at the distal tip. The tethered portion contains a single mode optical fiber multiplexed to three laser diodes at the proximal end. This design offers two main advantages over current endoscope technology. First, because of its small size, the TCE can be swallowed with minimal patient discomfort, thereby obviating sedation. Second, by imaging via directed laser light, the TCE is strategically positioned to employ several burgeoning laser-based diagnostic technologies, such as narrow-band, hyperspectral, and fluorescence imaging. It is believed that the combination of such imaging techniques with novel biomarkers of dysplasia will greatly assist in identifying precancerous conditions such as Barrett's esophagus (BE). As the probe is swallowed, the fiber scanner captures high resolution, wide-field color images of the gastroesophageal junction (500 lines at 0.05-mm resolution) currently at 15-Hz frame rate. Video images are recorded as the capsule is slowly retracted by its tether. Accompanying software generates panoramic images from the video output by mosaicing individual frames to aid in pattern recognition. This initial report describes the rationale for the unique TCE system design, results from preliminary testing in vitro and in vivo, and discussion on the merits of this new platform technology as a basis for developing a low-cost screening program for esophageal cancer.     

单元探测器的短波红外多通道成像技术

为了克服目前利用短波红外焦平面器件获取图像时难以消除器件自身的非均匀性、难以获得较高信噪比及成本昂贵的问题,提出了利用单元探测器和DMD(Digital Micro-mirror Device)空间光调制器件,基于Hadamard变换进行凝视光学画幅式成像的方法.通过实验验证了该方法用于短波红外成像的可行性.对实现低成本、高信噪比的短波红外成像具有借鉴意义.     

Analysis of false alarm for imaging space-based laser warning system

In view of the problem of false alarm in imaging space-based laser warning system, the effects of sunlight and lightning on the threaten laser detection and attack event determination are studied by analyzing and calculating the radiant energy density and space-time feature of imaging spot, respectively. The results show that the main false alarm resourses of spacebased laser warning system are sunlight and lightning. The sunlight should exposure the detector directly in one ninth of the satillite orbital period, and the imaging spot of sun is similar to the attack laser. The lightning imaging spot is similar to the illumination laser. About 1.4 lightning events can occur in the field of view (FOV) of the warning system per second. It could not discriminate spots of sun, lightning and threaten laser by the frame subtraction technology.     

同步扫描水下激光成像系统主要光学参数的理论分析

本文介绍了距离选通和同步扫描两种水下激光成像技术发展现状。从理论上计算了同步扫描系统的信号光和后向散射光传回到探测器端的辐照度与衰减长度的定量关系。减小视场角和增大光源到探测器的间隔可提高成像距离。一般水质下成像距离理论值约１２倍衰减长度。     

轻小型机载激光扫描仪设计

介绍了作为机载激光雷达关键部件的激光扫描仪模块化设计方法和各模块主要功能。为实现激光扫描仪的小型化、轻量化目标,设计了四面棱镜作为扫描部件,分析了工作距离与光学口径的对应关系并基于探测器参数设计通光口径,采用光纤激光器作为光源有效减小了扫描仪的尺寸和功耗,并设计了准直系统对出射激光进行整形。在16 m距离和293 m距离的定点测距地面测试中,轻小型激光扫描仪精度可达到5 mm和18 mm,最后介绍了搭载轻小型激光扫描仪进行的飞行实验结果。     

棉结在线检测系统中的光源选择

梳棉机棉结检测系统是基于机器视觉理论提出的一种新型在线检测系统。光源在系统中起到照明的作用,是影响棉结检出率的重要因素。为满足棉结在线检测系统宽幅面、高速和高分辨率的检测要求,需要对光源系统进行优化设计。通过实验可以获知棉网上的棉结对何种波长范围的光具有最大的反射率,以及棉结和周边结构如何获得最好的对比度。在比较了传统的荧光灯、高压汞灯和发光二极管(LED)线光源的光谱曲线后,提出了采用He-Ne激光器与光学系统配合后进行照明的光源设计方案。实测结果表明.由于激光束的高亮度和高准直性的优点,这种光源较其他光源更适合棉结检测照明的实际环境,可以满足检测需要。     

PSD及其在非接触测量中的应用

介绍了一种光电位敏探测器PSD及其在非接触测量中的应用,同时给出测量原理和PSD的前置适配电路.     

W-band Imaging Detector with Incoherent Illumination

A single-pixel imaging detector operating in W-band is described. It is based on a wideband receiving module using direct detecting circuitry and a transmitting unit with a pulse-modulated wideband noise source. The detector consists of a single transmit / receive channel mounted on a programmable scanner in an X-Y plane configuration. A LabView interface integrated with MatLab is employed allowing image continues reconstruction line-by-line. The application of incoherent illumination generated by a frequency-limited noise source improves image quality compared with conventional coherent sources used in active imagers. An image processing algorithm using a binary threshold level is considered with some examples of image reconstruction employing the detector.     

扫描非均匀性对点目标探测影响

为了深入研究物方扫描机构与点目标探测性能的关系,定义了度量扫描机构运动特性的扫描非均匀性指标。根据扫描成像的物理过程,建立了线阵探测器扫描成像模型,并以目标信噪比为核心分析了TDI探测器下扫描非均匀性的影响。首先,根据物方扫描工作特点设置了与扫描机构工作方式相配合的探测器积分时序,并建立了扫描非均匀性度量参量;其次,在经典成像模型的基础上建立了符合积分时序和TDI工作原理的点目标成像模型,并结合探测器噪声模型和TDI工作原理推导了目标信噪比计算公式,通过该公式分析了不同光学系统、TDI级数及目标尺度条件下目标信噪比与扫描非均匀性的关系;最后,从保证能够目标检测性能的角度给出了在相对信噪比限制条件下扫描非均匀性上限。所建立的成像模型准确反映了扫描探测系统各部分特性,分析结果对探测系统的总体设计和指标分配具有指导意义。     

基于盖革APD阵列的微扫描激光成像技术

盖革APD阵列探测的激光成像雷达具有高灵敏度、高帧频、宽视场、坚固、体积小等优点,成为了激光成像雷达发展的趋势。但目前APD阵列像元填充比低,器件阵列少,无法满足高分辨率激光成像的要求。为了解决该问题文中提出采用激光点阵发射的方法与APD阵列像元一一对应,采用拼接技术提高成像分辨率,采用微扫描技术提高激光成像视场。通过构建实验系统,完成了室外试验,成像效果良好,使用现有APD探测器（3232）将系统空间分辨率提高了四倍（6464）,提高了激光三维成像能力。     

532nm激光距离选通成像系统

实现了一套基于532 nm波长的距离选通成像系统,并选择了几种典型环境进行了相应的原理验证实验。采用532 nm的全固态调Q脉冲激光器作为主动照明激光,激光单脉冲能量可以在35~100 mJ之间调节,系统接收望远镜口径为200 mm。采用PIN探测器获得激光脉冲发射时间,并控制目标成像的曝光时刻。成像探测器采用ICCD(intensified CCD),最小曝光时间为2 ns。通过实验对比说明该系统能够在小雨天或者有烟雾的情况下正常工作,但是获得图像的信噪比会有所下降,同时能够在强光背景干扰的环境下获得目标的图像信息。该套系统的原理验证性实验能够为距离选通成像技术的进一步发展提供重要参考。     

人肺组织内源性显微荧光特性研究

采用新型显微荧光分光光度系统 ,实现激光诱导人肺组织内源性显微荧光光谱与图像的测量 ,获得不同组织层 (即上皮层 ,粘膜层和软骨层 )的荧光分布和荧光特性 ,为探索癌与正常组织自体荧光光谱特征差异的根源 ,揭示激光诱导自体荧光法诊断和定位早期肺癌的机理提供重要的实验依据     

MATLAB在水下激光线扫描图像处理中的应用

MATLAB在数字图像处理中的应用越来越广泛。首先需要对水下激光线扫描系统成像获得的原始试验数据进行视频及图像处理才能完成对目标信息的重建。然后利用数学形态学方法进行图像处理,去除图像的背景光噪声。再用直方图均衡实现图像增强。实验结果表明应用MATLAB对图像进行形态学、直方图调整等方法能够有效消除图像的背景光噪声,提取出目标信息,提高信噪比,对水下激光成像效果的改善有显著效果。同时,相当于增大了水下激光成像的探测距离。     

新体制激光雷达光纤扫描系统

为了提高激光成像雷达的帧频与激光点斑密度,介绍了光纤扫描装置的原理。光纤扫描激光雷达系统基于两套激光发接收对称的光纤束,其发射系统由圆形排列到线性排列、接收系统由线性排列到圆形排列;圆形排列激光束与扫描摆镜、直线排列光纤束与物镜系统分别构成发收光学系统,实现光束在空间的偏转和接收。该雷达的核心是光纤束与光学镜头耦合构成的发收光学系统以及相应的控制系统。重点分析了光纤的数值孔径、瞬时视场角、成像视场、光学耦合效率等光学系统参数设定方法,介绍了一种光学镜头设计方案及控制系统中MCU的功能和参数选择方法。该项研究结合了国内的光学超精细加工、精密光学装调以及同步控制技术水平等设定合理的参数,概念新、方法新,实现光纤扫描激光雷达还是可行的。     

主光轴平行于基底的微透镜阵列制作与测试

应用SU-8负性感光胶的独特性能,采用水浴倾斜紫外光刻的方法,优化工艺参数,构造出主光轴平行于基底的球面微透镜阵列,其单个透镜的直径约为200μm。利用激光扫描共聚焦显微镜(LSCM)对微透镜的表面形貌及曲率半径进行测量,并搭建光学观测平台,测得透镜焦距并观察成像效果。经观测,所加工球面微透镜具有较好的表面形貌和成像效果。基于此方法加工的微透镜阵列,主光轴平行于基底,因而便于与其他光学系统进行片上集成,完成对光线的聚焦,最终实现光开关、扫描成像等功能。此微透镜阵列也将集成在微流式细胞仪上,用于样本流的荧光检测,可极大提高检测精度。     

红外点目标成像信噪比建模分析

点目标的探测是红外成像探测系统的重要课题。以点扩散函数作用下点源目标像的照度分布函数为基础,综合考虑像的照度分布与单元探测器的位置关系,结合探测器的光电转换原理,建立了红外焦平面探测器点源光信号到电信号的转换关系;并在此基础上结合探测器的噪声模型,建立了点源信噪比模型。仿真计算结果表明:点源目标的探测信噪比与光学系统点扩散函数、单元探测器尺寸、视线偏移密切相关。该研究可为点目标红外成像探测距离的精确估计提供理论支持。