双纵模双频激光精密测距仪的研究

介绍了一种双纵模双频激光精密测距的工作原理,信号处理及误差分析。测距仪是以频差800MHz(对应波长长度为380mm)的波长为测量基准进行测量的,对不足半个波长的长度是利用双频激光干涉仪的原理进行测量的。对该测量方法精度的理论和实验研究后,可以确定出总的测量精度为±(50±1.5×10-6L)μm。     

基于双通道可调F-P干涉仪的机载测风激光雷达系统的鉴频器

利用双通道可调Fabry-Perot干涉仪作为机载测风激光雷达系统的鉴频器。该鉴频器可以克服现有测风雷达测速范围小的缺点,能够根据相对风速变化调整干涉仪的腔长,从而达到调整干涉仪透射谱中心频率的目的,从而间接实现测速范围动态可调,扩大测速范围的目的。采用此鉴频器可以实时测量飞行器与大气的相对风速。文中详述了测速原理和鉴频器结构,并给出机载雷达的系统参数,分析了系统的测量误差,结果表明:探测累积时间1s,测速范围为0~1000m/s时,探测高度可达30km,系统测量误差小于5m/s。     

He-Ne激光器纵模分析实验

为了很好地验证纵模频率间隔与激光谐振腔长度之间的关系,实验中改变光学谐振腔的长度,纵模频率间隔相应地发生改变,把某一腔长下的纵模频率通过共焦球面扫描干涉仪将激光器模式输出到示波器进行显示。通过对示波器显示的频率—时间图进行分析,可以测出一定腔长下激光纵模的频率间隔,该测量值与理论计算值基本一致。     

激光干涉仪的信号处理系统——激光干涉仪技术综述之三

介绍了激光干涉仪的信号处理方法,分析了单频激光干涉仪中消除直流漂移的方法,双频激光干涉仪中的减法器、频率解调、相位解调技术的特点。     

双频激光干涉仪中的数字相位计设计

基于Altera公司FPGA芯片,提出了一种基于双频激光干涉仪系统中数字相位计的实现方法。该相位计用于测量系统中被测信号和参考信号之间的相位差角度,间接测量激光干涉仪的光程差信息。被测信号经过光电接收器以及A/D模数转换成数字信号送到FPGA芯片中,与FPGA内建的查找表参考信号做正交相关法解调运算,得到一组X-Y值,再利用CORDIC算法计算arctan函数获取相位差,最后计算出干涉仪的光程差,算法的全过程使用FPGA硬件实现。实验结果表明,该相位计使双频激光干涉仪的相位差测量精度在0.01°以内。     

高功率液压驱动系统测速方法的改进

高功率液压驱动系统测速部分一般采用测速发电机测量转速,但这种方法故障率高,严重影响液压系统的安全稳定运行。本文给出了一种齿轮测速的方法,将转速信号转化为脉冲频率信号进行测量和显示。结果表明,改进后的测速系统精度可以满足要求,故障率大大降低。     

双频激光合成波长干涉仪的精确定位方法研究

本文构筑了一种在同一干涉仪中可同时实现大范围和高精度纳米测量的双频激光合成波长干涉仪;针对该干涉仪的光路结构特点,提出一种新的粗精定位相结合的干涉信号同相位检测方法,实现了对不同频率干涉信号的同相位检测;实验测量结果表明该定位方法能够实现0.41nm的定位精度.     

激光干涉仪的基本类型——激光干涉仪技术系列综述之一

分析了几种典型的激光干涉仪系统的原理和特点,介绍了基于双折射—塞曼双频激光器,输出频差在3-40MHz范围,是外差激光干涉仪最合适的使用频段,具有很好的应用前景。     

Elden公式法在双频激光干涉仪测量系统的应用

双频激光干涉仪测量系统是以激光波长为测量基准,在空气中传播的激光波长会受到空气折射率变化影响,分析了现有的激光波长补偿方法,重点对间接补偿法中的Edlen公式法进行了研究。搭建了一套双频激光干涉仪测量的实验平台,并对不同光程下实验平台的稳定性进行了测试,结果表明:实验平台的测量值能达到m量级,具有较好的稳定性。采用高精度的温度传感器和压力传感器实时测量环境参数,完成Edlen公式法的补偿实验,实验结果表明:当存在一定外界环境影响时,Edlen公式法的纳米级测量补偿效果能提升10~(-10)m量级;在实际应用中的微米级环境测量情况下时,补偿效果能提升10~(-8)m量级。     

双频激光干涉仪的原理与应用（一）

双频激光干涉仪的原理与应用（一）机械部成都工具研究所（６１００５６）羡一民编者按双频激光干涉仪是在单频激光干涉仪的基础上发展的一种外差式干涉仪。被测信号载波在一个固定频差上、整个系统成为交流系统．大大提高了抗干扰能力，特别适合现场条件下使用。仪器与不...     

激光显示中声光调制器的研究

激光显示系统中常采用高速宽带声光调制器调制激光光强,使衍射光束的光强随视频信号变化,系统要求调制器具有很快的响应速度和很高的衍射效率。采用熔石英作为声光介质,铌酸锂作为换能器,设计并制作出工作中心频率为180MHz,调制频率为32MHz,衍射效率达75%的高速宽带声光调制器。并设计了一套使激光光源和声光调制器相匹配的光学系统,在优化激光束聚焦的基础上提高调制速度。设计的高速声光调制器基本满足了激光显示的要求。     

基于DSP的宽动态范围莫尔条纹计数与精密细分技术

为莫尔条纹的计数与细分提供了一种基于DSP(数字信号处理器)的高速软件解决方案。它能有效的解决传统系统中计数电路与细分功能不能无缝匹配的问题,提高测量的准确性。由于采用了高速信号处理和闪烁采样技术,采用该方案的系统能处理宽动态范围的莫尔条纹信号。提供的实例能对从直流到1MHz的莫尔条纹信号进行计数与细分,对于1μm光学分辨率的光栅测长系统来说,其相应的最高测量速度为1000mm/s,细分步长可以达到nm级。     

相位法激光测距接收系统

相位法激光测距作为一种高精度的测距方法,在很多领域中得到广泛应用,在激光调制频率一定的情况下,测距速度和精度取决于相位差测量的速度和精度,并受信号串扰等因素的影响。基于此,提出了一种新的相位差放大测量的方法,在不增加测量时间的同时将测相精度提高1/N倍,并结合欠采样技术避免了混频器和其他多余器件的使用,减小了串扰对系统的影响;高频弱光信号入射到雪崩光电二极管上,会在输出信号上产生相位延迟导致测距误差,我们提出灵活控制加在雪崩光电二极管上的反向偏压的方法减小该相位延迟,对于调制频率为18.5MHz波长为650nm的激光,当入射光强度为0.5uW时,可将相位延迟从1.4度 压缩到0.03度 之内;建立了信号串扰产生测相误差的数学模型,并通过实验给出了采取不同屏蔽措施时串扰对测相误差的影响。实验结果证明,当调制频率为18.5MHz时,测相精度为0.014度 ,相应测距精度可达0.3mm 。     

多方式协同He-Ne激光器稳频系统设计

将传统双纵模热稳频技术与电磁感应涡流加热稳频技术相结合,设计了He-Ne激光器稳频系统,该He-Ne激光器既具有双纵模热稳频技术长时间稳定性好的特点,又具有电磁感应涡流加热稳频技术响应速度快、抗干扰能力强的特点,当输出双频激光频差大于500 MHz时可实现高速在线测量。     

重复频率锁定的783 nm飞秒光纤激光器研制

设计并搭建了重复频率长时精确锁定的783 nm飞秒光纤激光器。该激光器基于全保偏非线性干涉环镜(NALM),实现掺铒光纤振荡器锁模脉冲输出,由与脉冲分离器级联的环境稳定掺铒光纤双级放大器进行功率放大,实现了平均功率1.30 W、脉冲宽度130 fs、重复频率77.1 MHz、1 560 nm脉冲输出;通过周期极化铌酸锂(PPLN)光学晶体倍频,获得了平均功率为0.52 W、脉冲宽度为140 fs、783 nm脉冲输出。通过重复频率监测及锁相环技术,进一步将掺铒光纤振荡器的重复频率溯源至参考铷原子钟,12 h内频率抖动峰-峰值为5 mHz、标准偏差为1.2 mHz。该激光器系统具有稳定性高、集成度高、体积小的特点。     

高精度可连续调节宽带猝发信号发生器设计

本文设计了一种使用纯硬件的设计方法，实现低失真率，频率精度高，且产生连续可调的猝发信号。使用模拟乘法器调幅和模拟开关关断实现矩形窗、汉宁窗、海明窗等不同的加窗形式。另外猝发信号发生器采用了以单片机为核心的嵌入式控制系统，方便地上位机对信号发生器控制。通过串口通信上位机（个人计算机）可以在线修改信号发生器的猝发时间间隔，猝发脉冲宽度，以及信号频率。该信号发生器最高频率达1.8MHz，可以广泛应用于超声导波，电磁超声检测，以及激光脉冲控制等。     

Frequency discriminators for the characterization of narrow-spectrum heterodyne beat signals: application to the measurement of a sub-hertz carrier-envelope-offset beat in an optical frequency comb

We describe a radio-frequency (RF) discriminator, or frequency-to-voltage converter, based on a voltage-controlled oscillator phase-locked to the signal under test, which has been developed to analyze the frequency noise properties of an RF signal, e.g., a heterodyne optical beat signal between two lasers or between a laser and an optical frequency comb. We present a detailed characterization of the properties of this discriminator and we compare it to three other commercially available discriminators. Owing to its large linear frequency range of 7 MHz, its bandwidth of 200 kHz and its noise floor below 0.01 Hz(2)/Hz in a significant part of the spectrum, our frequency discriminator is able to fully characterize the frequency noise of a beat signal with a linewidth ranging from a couple of megahertz down to a few hertz. As an example of application, we present measurements of the frequency noise of the carrier envelope offset beat in a low-noise optical frequency comb.     

Modulated CMOS camera for fluorescence lifetime microscopy

Widefield frequency‐domain fluorescence lifetime imaging microscopy (FD‐FLIM) is a fast and accurate method to measure the fluorescence lifetime of entire images. However, the complexity and high costs involved in construction of such a system limit the extensive use of this technique. PCO AG recently released the first luminescence lifetime imaging camera based on a high frequency modulated CMOS image sensor, QMFLIM2. Here we tested and provide operational procedures to calibrate the camera and to improve the accuracy using corrections necessary for image analysis. With its flexible input/output options, we are able to use a modulated laser diode or a 20 MHz pulsed white supercontinuum laser as the light source. The output of the camera consists of a stack of modulated images that can be analyzed by the SimFCS software using the phasor approach. The nonuniform system response across the image sensor must be calibrated at the pixel level. This pixel calibration is crucial and needed for every camera settings, e.g. modulation frequency and exposure time. A significant dependency of the modulation signal on the intensity was also observed and hence an additional calibration is needed for each pixel depending on the pixel intensity level. These corrections are important not only for the fundamental frequency, but also for the higher harmonics when using the pulsed supercontinuum laser. With these post data acquisition corrections, the PCO CMOS‐FLIM camera can be used for various biomedical applications requiring a large frame and high speed acquisition. Microsc. Res. Tech. 78:1075–1081, 2015. © 2015 Wiley Periodicals, Inc.     

相位式激光测距谱分析鉴相的无偏改进

针对相位式激光测距中的鉴相误差,建立了谱分析鉴相的误差模型,提出了在数据预处理中引入希尔伯特变换来消除相位差估计偏差的测量方法.分析了传统谱分析鉴相的偏差和方差,指出这些测量偏差受初相位的影响,在高速测距中不容忽略.提出了一种无偏改进方法,通过窗函数法设计正弦信号的简易希尔伯特变换器,将离散傅里叶变换的对象转换为解析信号,在仅增加4次加减法运算和2次移位操作的情况下,实现了近似无偏谱分析鉴相.仿真分析和实验验证结果表明,鉴相均值与真实相位差相同;当信噪比为40 dB时,每秒百万次高速鉴相的误差为0.1°;当调制频率为100 MHz时,测距精度达到0.4 mm.实验表明,将希尔伯特变换应用于谱分析鉴相,可实现高准确度相位差测量,并可应用于高速相位式激光测距.     

Application of a high power Yb fiber‐based laser compatible with commercial optical parametric oscillator for coherent anti‐stokes raman scattering microscopy

Coherent anti‐Stokes Raman scattering (CARS) microscopy is a powerful tool for chemical analysis at a subcellular level, frequently used for imaging lipid dynamics in living cells. We report a high‐power picosecond fiber‐based laser and its application for optical parametric oscillator (OPO) pumping and CARS microscopy. This fiber‐based laser has been carefully characterized. It produces 5 ps pulses with 0.8 nm spectral width at a 1,030 nm wavelength with more than 10 W of average power at 80 MHz repetition rate; these spectral and temporal properties can be slightly modified. We then study the influence of these modifications on the spectral and temporal properties of the OPO. We find that the OPO system generates a weakly spectrally chirped signal beam constituted of 3 ps pulses with 0.4 nm spectral width tunable from 790 to 930 nm optimal for CARS imaging. The frequency doubling unconverted part is composed of 7–8 ps pulses with 0.75 nm spectral width compatible with CARS imaging. We also study the influence of the fiber laser properties on the CARS signal generated by distilled water. In agreement with theory, we find that shorter temporal pulses allow higher peak powers and thus higher CARS signal, if the spectral widths are less than 10 cm^?1. We demonstrate that this source is suitable for performing CARS imaging of living cells during several hours without photodamages. We finally demonstrate CARS imaging on more complex aquatic organisms called copepods (micro‐crustaceans), on which we distinguish morphological details and lipid reserves. Microsc. Res. Tech. 77:422–430, 2014. © 2014 Wiley Periodicals, Inc.