旋转体表面轮廓测量的激光多普勒信号研究

在利用激光多普勒效应对旋转体表面轮廓损伤进行测量时，其散射光的多普勒信号强度及质量是影响测量精度的极其重要的参数。研究了激光多普勒参考光技术、旋转体表面散射光位相无规则变化的平均效应和最小二乘法曲线拟合技术，设计出高信噪比的参考光路，并对物体表面细微结构所引起的信号丢失进行了重构，实现了旋转体表面轮廓损伤的测量，其相对误差约0．3％。     

激光多普勒技术测量大尺寸直径的研究

介绍了激光多普勒技术用于大尺寸直径测量的原理 ,并据此设计了新型差动激光多普勒大尺寸直径测量系统。采用差动型光学系统并使用声光调制器对测量光束进行调制 ,提高了系统的测量精度。高频信号和低频信号分开处理 ,消除了信号的相互干扰。实验结果反映了系统良好的线性度。线性回归的相关系数达到 0 .9999,相对测量精度为 3× 10 - 4 。     

Evaluation of a Laser Doppler Flowmeter for Measurement of Tissue Blood Flow

An instrument for measurement of tissue blood flow based on the laser Doppler principle was evaluated using a fluid model. A unique and linear relationship between flowmeter response and flux of red cells was demonstrated with red cell velocities and volume fractions within the normal physiological range of the microcirculatory network of the skin. Different degrees of oxygenation proved to influence the Doppler signal only to a minor extent. The study also shows that the Doppler signal is formed essentially by heterodyne mixing of light beams backscattered in static structures and moving red cells.     

利用微波调制激光技术测速的实验研究

为了验证微波调制激光技术进行速度测量的可靠性,构建了一套通过微波调制激光技术测速的实验系统。利用激光作为载波,微波作为模拟调制信号对激光信号进行强度调制,光电探测器对信号光强度进行直接探测。利用射频电路,获得多普勒频移数据反演发射端和接收端相对运动速度。同时通过测量运动距离和时间计算平均运动速度,作为第三方数据,用于与微波调制激光技术测速的数据进行比较。理论分析了这套系统的原理并对其进行了实验验证。实验结果表明,利用微波调制激光技术测速的数据与第三方数据平均偏差小于2.0%,符合性好。     

Integrated optoelectronic probe including a vertical cavity surface emitting laser for laser Doppler perfusion monitoring

An integrated optoelectronic probe with small dimensions, for direct-contact laser Doppler blood flow monitoring has been realized. A vertical cavity surface emitting laser (VCSEL), and a chip with photodetectors and all necessary electronics are integrated in a miniature probe head connected to a laptop computer. The computer sound processor is utilized for acquisition and digital signal processing of the incoming Doppler signal. In this paper, the design of the laser Doppler perfusion monitor is described and its performance is evaluated. We demonstrate our perfusion monitor to be less sensitive to subject motion than a commercial fiber-optic device. For medium and high perfusion levels, the performance of our integrated probe is comparable to the fiberoptic flowmeter containing a normal edge-emitting laser diode. For very low perfusion levels, the signal-to-noise ratio of the fiber-optic device is higher. This difference can mainly be attributed to the shorter coherence length of the VCSEL compared with the edge-emitting laser diode.     

8C2--Fluid flow measurements with a laser Doppler velocimeter

The basic principles of the laser Doppler velocimeter, a new instrument for measurement of localized flow velocities in gases and liquids, are discussed in detail. Velocity measurements are made by detecting the Doppler shift in monochromatic laser light which is scattered from small contaminant particles in the fluid. ACWgas laser serves as the light source, and the Doppler shift is detected by optical heterodyne techniques. The latest fluid flow measurements obtained with the laser Doppler velocimeter are presented.     

激光结构光测量连续调节智能光源控制器设计

激光结构光视觉测量过程中被测物体的表面材质差异、表面几何曲率大小均会影响到实际采集的激光光斑图像质量,从而影响到测量数据处理的精确度和准确性。为了适应工业测量中多变的被测对象特性和使用环境,对结构光源的激光二极管进行电流控制。在分析mW级别小功率激光二极管工作特性的基础上,提出了一种使用上位机和ARM微控制器的微小功率半导体激光器智能控制器的低成本设计方案。研究了数字PWM信号驱动激光二极管的技术,使用ARM微控制器生成PWM信号输出,然后PWM数字信号通过光电隔离的阻容滤波电路、运放电压跟随、调理电路以及压控恒流源电路(V-I)驱动半导体激光二极管的电流大小。激光控制器的PWM信号的占空比、基准频率通过上位机串行Modbus协议通讯进行快速设定。系统经过激光结构光投影成像实验进行验证,适时调整激光结构光输出强度大小,可优化激光视觉测量系统的测量输出和适应性。通过实验验证的结果表明,系统可以稳定运行。     

DRNN在激光多普勒测振仪测声系统中的应用

为了降低激光多普勒测振仪在测声过程中给语音信号中引入的噪声，采用深度循环神经网络语音信号去噪的方法，对从激光多普勒测声系统采集回来的语音信号做降噪处理，并进行了理论分析和实验验证。结果表明，利用层数为1层~3层、每层神经元个数为1024的深度循环神经网络，对-6dB~6dB信噪比的语音信号进行处理，随着层数的增加，语音信号的质量在多项评价指标上达到8dB~12dB的提升; 深度循环神经网络可以有效对激光多普勒测声系统采集的语音信号进行降噪处理。该研究对提升语音信号的质量有着实际意义。     

基于激光的多相流测试技术应用研究进展

激光测速已广泛存在多相流动测量中,测量原理主要有相关性原理和多普勒原理,将两种测量原理分别与成像技术或光散射理论结合发展了多种测试技术。本文对基于激光的多相流测试技术在多相流动测量应用研究进展进行分析和综述,并对今后发展进行展望。粒子成像测速技术、激光多普勒测速仪、相位多普勒风速计等已成为多相流动参数测量的有效工具,激光诱导荧光技术在工程多相流动相分离领域应用前景较好。随着对多相流动机理认识的加深,三维粒子成像测速技术、全息粒子图像测速技术等将是今后多相流动测量领域发展的热点。     

Laser Doppler velocimetry: A status report

Since the first experimental work in 1964, the measurement of velocity by means of the Doppler shift in scattered laser light has developed into an important tool in fluid mechanics research which often provides data unobtainable with other instruments. This paper reviews the fundamentals of laser Doppler velocimeter system design including optical requirements and signal processing considerations. Numerous applications are described to illustrate the present state of the art.     

A new instrument for continuous measurement of tissue blood flow by light beating spectroscopy

A new instrument for measurement of regional tissue blood flow based on the laser Doppler principle is reported. The theoretical background of light beating spectroscopy is discussed and a detection technique which makes possible the suppression of the adverse effects of laser-mode interference and wide-band beam amplitude noise is described. Instead of using a single square-law photodetector a differential detector technique is introduced that reduces common-mode noise to a negligible level, without influencing the blood flow related signal. The new instrument has proved to be highly stable and sensitive. Continuous recordings of tissue blood flow can be performed in the laboratory as well as at the bedside.     

PDH激光稳频控制技术研究

针对多普勒测风激光雷达系统的应用需求,研制了一套结构紧凑、操作灵活的Pound-Drever-Hall(PDH)激光稳频系统。直接数字频率合成器(DDS)产生激光器高频相位调制信号,模拟混频器解调激光器的频率漂移信息,高集成度的数字信号处理器(DSP)作为稳频控制系统的心脏,负责整个稳频系统的总线控制、信号处理及比例积分微分(PID)伺服等。实验表明,在2.5h内激光器的相对频率漂移不超过±17kHz,其均方根(RMS)误差为5kHz,绝对频率稳定度优于200kHz。在主动对法布里-珀罗干涉仪(FPI)施加6 Hz固定扰动时,系统能够在30ms内迅速恢复稳定。满足直接探测多普勒测风雷达系统中0.1m/s测风精度的应用需求。     

一种便携式激光多普勒测速光学系统的设计

为了将激光多普勒测速技术应用于野外流体速度测量,设计了一种基于舣光束模式的激光多普勒测速光学系统,采用光纤耦合半导体激光器作为光源,通过保偏光纤耦合器、保偏光纤准直器以及非球面透镜来实现激光的分束、准直与聚焦,形成干涉条纹,并利用接收透镜、针孔光阑以及雪崩光电二极竹检测多普勒信号光.结果表明,所设汁的光学系统的空间分辨...     

Coherent laser radar in Europe

European work in coherent laser radar with 10 μm and shorter wavelength lasers is reviewed. Fundamental aspects include heterodyne studies of signal statistics and fluctuations, and detailed experimental and theoretical work on signal amplification and autodyne arrangements with light reinjected into the laser cavity. Progress with lasers, detectors, and modulators has led to the development of several compact robust field systems both continuous-wave and pulsed. Various ground-based programs are described including local wind field measurement and wake vortex investigation at airfields, and study of range, image, and Doppler shift of hard targets. Airborne systems have investigated avionics problems of true airspeed, pressure error, and wind shear warning. Other airborne studies include ground imaging, obstacle warning, terrain following, and a compendium of atmospheric backscattering over the North and South Atlantic. In recent years, the European Space Energy has supported studies and technology development for a space-borne wind lidar in the Atmospheric Laser Doppler Instrument (ALADIN) program     

电缆激光多普勒在线计米系统研究

为了满足电缆生产过程中长度在线测量的需要,设计了基于激光多普勒测速原理的电缆长度在线计米系统。阐述了激光多普勒测速基本原理,设计了一种结构紧凑的双光束双散射型光路。提出了基于有限长单位冲激响应（Finite Impulse Response,FIR）滤波器的滤波带自适应选择算法,有效地滤掉基底信号和部分噪声,减小了多普勒信号噪声的影响,改善了信噪比;利用能量重心校正技术进行频谱校正,减小了系统的测量误差。搭建了实验装置,进行了对比测量实验,实验结果表明:该系统能实时、准确的进行长度在线测量,相对误差小于0.1%。     

A laser speckle imaging technique for measuring tissue perfusion

Laser Doppler imaging (LDI) has become a standard method for optical measurement of tissue perfusion, but is limited by low resolution and long measurement times. We have developed an analysis technique based on a laser speckle imaging method that generates rapid, high-resolution perfusion images. We have called it laser speckle perfusion imaging (LSPI). This paper investigates LSPI output and compares it to LDI using blood flow models designed to simulate human skin at various levels of pigmentation. Results show that LSPI parameters can be chosen such that the instrumentation exhibits a similar response to changes in red blood cell concentration (0.1%-5%, 200 microL/min) and velocity (0-800 microL/min, 1% concentration) and, given its higher resolution and quicker response time, could provide a significant advantage over LDI for some applications. Differences were observed in the LDI and LSPI response to tissue optical properties. LDI perfusion values increased with increasing tissue absorption, while LSPI perfusion values showed a slight decrease. This dependence is predictable, owing to the perfusion algorithms specific to each instrument, and, if properly compensated for, should not influence each instrument's ability to measure relative changes in tissue perfusion.     

零差激光测振系统中含噪多普勒信号处理方法

针对零差激光测振系统中多普勒信号的噪声导致信号正交校正困难、增大测量误差的问题,提出了含噪多普勒信号处理方法。首先利用平滑滤波对两路含噪多普勒信号进行降噪处理,再通过最小二乘法对非正交多普勒信号进行校正,然后采用单位圆校正算法二次校正成正交信号,最后利用微分相除积分操作解调出振动信号。实验结果表明,本文方法能有效解调振...     

激光多普勒检波系统的研究

为了进一步提高地震检波器的指标,研究了激光多普勒测量方法和微弱信号检测技术等,设计出了一种LD做光源的差动式激光多普勒检波系统,此系统采用高斯光束聚焦、大口径透镜接收,能接收到很强的多普勒信号,并且具有高的空间分辨力,同时,采用声光调制技术及锁相放大技术,提高了信号的信噪比,其结构简单、紧凑,装调方便,光能利用率和空间分辨力高,可测频率范围为0.5Hz～1000Hz;振幅范围为2μm～5mm;频率测量精度为0.6%;振幅测量精度为1%。     

反向重投影多线结构光立体视觉测量方法

研究了多线结构光立体视觉测量系统中激光条纹中心点的匹配问题。系统测量过程中,将两幅图像的激光条纹中心点通过重投影相互匹配,计算对应的三维空间点。针对一个激光条纹中心点存在多个匹配点的问题,提出了反向重投影的方法。该方法将匹配点反向重投影到原激光条纹图像,利用光路一致性,筛选出唯一匹配点。另外,分析了在重投影和反向重投影时采用不同大小的匹配窗口对测量结果的影响。实验表明,该方法能够充分利用激光条纹中心点,同时又有较高的唯一匹配率,明显提高了系统的测量效率。     

基于空域变换的超分辨成像系统

传统的超分辨成像系统易受外界环境影响,抗噪效果差,输出的超分辨图像清晰度较低,基于此设计基于空域变换的超分辨成像系统,系统先将激光集中在孔径光栏上射出,通过聚光镜汇聚激光,根据分光镜和辅助镜将激光聚焦在显微镜焦平面上,依照物镜将激光束转变成平型光,使平行光能够均匀照射测量样品上,采用显微镜和辅助物镜处理从样品表面反射的带有样品信息的激光,最后通过分光镜反射带有信息的激光,反射光束在CCD上显示成像,核心处理器是FPGAWie的图像采集模块,采集CCD传输的视频图像后,通过通用并行接口将采集的视频图像数据传输到图像处理模块,该模块通过空域变换方法处理图像,获取超分辨图像,最终传输到计算机上进行显示。经过实验分析发现,该系统图像稳定性和图像清晰度平均值分别是98. 538%和99. 19%,干扰信噪比为16 d B时,该系统成像时间最短为6. 57 ms,说明该系统成像清晰度高、抗干扰性能优。