基于希尔伯特变化的微小振动激光多普勒信号处理

为了实现对固体目标微小振动参数的测量,建立了微小振动的激光多普勒信号模型。采用希尔伯特数字运算,将激光多普勒振动信号的即时信号采样转化为信号的谱采样。通过频谱计算得到每个振动周期中瞬时频率的平均数,应用差值采样序列积分计算得到振动频率,最后根据振动信号频率变化与振幅的关系得到振幅。采用希尔伯特方法对实验测试结果进行处理验证,并分析了误差来源。实验结果表明：实验测量目标的振动振幅约为1.85×10-4m,转动的圆频率约为170 Hz。因此,应用希尔伯特变换方法处理测量的目标微小振动信号,获取目标运动的参数是可行的。     

光学系统受迫振动的激光测量方法

将激光信号与高帧频CCD结合,解决了光学系统中振动信号和激光信号之间的转换问题,不仅能够测量振动对系统光束指向稳定性的影响,而且能够得到振动信号本身的频率特性。利用该方法对振源为150 Hz和200 Hz两种条件下的光学系统受迫振动进行测量,得到了与输入信号相吻合的振动信号属性。通过实验与分析得知:时域振幅测量精度为6.25 m,频域分辨力为2 Hz,方法简便高效,测量结果准确,已应用于角多路准分子激光主振荡功率放大器系统打靶试验平台光束指向稳定性的研究中。     

振动对面形测量误差的影响分析

振动会使高精度面形测量产生误差。建立了振动对干涉测量面形的误差模型,应用13步移相算法分析了在振幅为63 nm时的误差情况。分析结果表明,当面形测量误差的敏感频率为12 Hz时,振动引起的面形均方根(RMS)误差约为12 nm。通过实验进行了验证,仿真分析结果和实验结果基本相同。实验分析了在12 Hz时,振幅为5~63 nm时,对应的测量面形RMS误差为1~7.1 nm,振幅和RMS误差线性增大。为不同振动频率和振幅引起的面形RMS的误差分析和高精度面形测量的振动环境控制提供了一定的参考。     

一种提高时间平均数字全息测振条纹模式对比度的方法

针对基于时间平均数字全息法的微振动原位检测,提出了一种有效提高振动条纹模式对比度的方法,进而可准确获得待测面振幅分布.首先针对实际振动过程中物体存在纵向微位移而引起的相位误差进行校正;然后去除记录过程中物光场散斑引起的相位噪音,有效提高了被第一类零阶贝塞尔函数调制的条纹对比度;最后利用第一类零阶贝塞尔函数的变化规律和条纹级数,定量估计全场的振幅分布.搭建了以声波作为激励源的时间平均全息测振实验系统,采用频率分别为0、1 100、2 000和9 000 Hz的正弦声波激励簧片进行实验验证.结果表明,以振动频率2 000Hz为例,本方法能够有效提高振动调制条纹质量,并计算得到三级零点处的振幅值分别为109.4nm、244.2nm、356.4nm,与理论值相比较,误差分别为6.31%、3.34%和3.78%,在允许范围之内,证明了该方法的有效性.     

弹载共孔径激光微多普勒目标识别系统研究

为实现对距离4 km目标100 Hz振动特征的提取,提出利用激光微多普勒手段增强导弹目标辨识能力的方法。设计了一种基于偏振分光的激光发射/接收/电视共孔径系统,这种能够二级稳定的系统适应于弹载环境,利用光纤选通完成光程自动补偿,实现相干光匹配,采用本振/回波信号相干法,用线宽300 Hz的本振光调制后形成探测脉冲光,可提高探测距离,并避免回波与本振光因大气衰减而导致的错峰,由FPGA/DSP构建的傅里叶变换电路可获取时频曲线信号,频移为36 kHz时可实现目标的辨识。     

降雨对532nm和1064nm激光传输的衰减特性研究

降雨会对激光信号产生严重的衰减,从而给激光目标探测的应用带来一定影响.激光在降雨中的传输衰减已在红外波段做了大量的实验研究,而可见光波段激光在雨中的传输衰减特性还未见报道.基于夫琅禾费衍射和几何光学散射理论,建立雨滴对532 nm绿激光和1064 nm近红外激光光束的传输衰减模型,对比分析两波长激光在不同降雨量下的衰减...     

基于不同频率成份衰减矫正的光声成像方法

根据超声衰减理论,研究了光声信号不同频率成份随距离的衰减差异,及其对光声图像重建的影响;提出了对光声信号不同频率成份进行衰减矫正的成像方法,此方法增强了光声信号的高频成份,突出了吸收体的边界变化和细微的结构特征,提高了成像系统分辨率,实验结果显示系统分辨率由0.3 mm提高到0.2 mm.实验所用的光源为YAG激光器,波长为1064 nm,重复频率为20 Hz,脉宽为6 ns,探测器为针状的PVDF膜水听器,接收面积的直径为1 mm.     

激光多普勒微振动信号的直接强度解调

在传统的激光多普勒测振方法中,频移信号的检测通常需要具有比较复杂的频率或相位解调系统。从激光多普勒频移和干涉理论出发,提出了一种测量振幅小于纳米量级的方法———直接强度解调法。分析了直接强度解调法的适用范围。实验中利用了迈克尔逊干涉仪结构,采用了直接强度解调的方法。对振幅约为1nm的振动信号来说,其信噪比为23dB。     

空中目标红外辐射多波长大气透过率实时反演算法

 针对空中目标红外辐射大气传输衰减的主导因素,通过Mie散射理论分析和计算得到了不同波长红外大气透过率之间的相关性关系。采用自主研发的激光遥感大气透过率测量仪并利用激光大气透过率多点断层测量技术,实测了1 060 nm波长激光的大气透过率,同步实时反演计算了临近波长红外辐射的大气透过率。实验数据验证了该方法可用于建立红外观测低空修正系统,实时计算获取大气对空间目标红外辐射的衰减特性。     

水下声辐射激励水表面声波的特征参数测量

采用激光干涉方法对水下声辐射激励水表面声波的特征参数频率和振幅进行了测量研究。从理论上对水表面声波激光相干测量信号的频谱构成进行了分析,在此基础上提出了水表面声波两个重要声学参数频率和振幅的解算方法,并通过数值仿真进行了验证。搭建了一套简单的激光干涉测量实验系统,对不同频率和声压激励的水表面声波进行了测量实验,验证了水表面声波频率和振幅解调方法的准确性。对水表面声波横向传播的振幅衰减现象进行了初步的实验研究,结果表明水表面声波的频率越高,振幅的横向衰减越快。研究表明激光相干检测方法能够准确地实现水表面声波振幅和频率的测量。     

Description of a coherent light technique to detect the tangential and radial vibrations of an arch dam

This paper describes a technique in which a laser light vibration sensor based on a Michelson interferometer is used. With a 5 mW laser the instrument will make measurements on a moving target at ranges greater than 200 m without using retro-reflective materials. Careful optimization of the electro-optic design reduces the effects of environmental disturbances and allows vibration amplitude resolution of 0·2 μm with a flat response in the bandwidth 0·1–150 Hz. Field tests and actual measurements of the radial and tangential displacements of an arch dam are shown.     

Detection of dust grains vibrations with a laser heterodyne receiver of scattered light

We present the results of measurement of grains vibrations under external action in gas and liquid with a laser heterodyne receiver of scattered radiation. For investigation of dynamic characteristics of particles we made the laser heterodyne receiver with sensitivity about 2×10⁻¹⁷ W/Hz and source of probing with radiation power 1 mW. In our pilot experiments, measurement of vibration amplitude of nanoparticles in gas (cigarette smoke) and microparticles in fluid (toothpaste in water) was made. We measured values of vibration amplitudes about 20–30 nm.     

A continuous-wave ultrasound system for displacement amplitude and phase measurement

A noninvasive, continuous-wave ultrasonic technique was developed to measure the displacement amplitude and phase of mechanical structures. The measurement system was based on a method developed by Rogers and Hastings ["Noninvasive vibration measurement system and method for measuring amplitude of vibration of tissue in an object being investigated," U.S. Patent No. 4,819,643 (1989)] and expanded to include phase measurement. A low-frequency sound source was used to generate harmonic vibrations in a target of interest. The target was simultaneously insonified by a low-power, continuous-wave ultrasonic source. Reflected ultrasound was phase modulated by the target motion and detected with a separate ultrasonic transducer. The target displacement amplitude was obtained directly from the received ultrasound frequency spectrum by comparing the carrier and sideband amplitudes. Phase information was obtained by demodulating the received signal using a double-balanced mixer and low-pass filter. A theoretical model for the ultrasonic receiver field is also presented. This model coupled existing models for focused piston radiators and for pulse-echo ultrasonic fields. Experimental measurements of the resulting receiver fields compared favorably with theoretical predictions.     

利用AOTF多光谱成像系统实现伪装目标的识别

针对传统分光器件存在移动部件以及不能快速实时选择波长的不足,搭建了用声光可调滤光器(AOTF)作为分光器件的多光谱成像系统。系统由光学镜头、AOTF、AOTF驱动器、CCD摄像机和图像采集系统组成。本系统能够在(500~1000)nm的光谱范围内成像。通过对AOTF的控制可以任意选择系统的光谱,从而有目的地选择具有典型目标特性的不同波段的光谱波长,形成同一目标在不同光谱波长下的不同图像。采用迷彩布、头盔以及自然花草进行多次目标特性识别试验,得到了能突出目标特性的具有典型光谱特性的图像。证实了基于AOTF的多光谱成像系统灵敏度高、体积小、无移动部件,并且能够快速实时地改变和选择光谱波段,在所成的多光谱图像中能提高目标与背景的对比度,对伪装目标有明显的探测和识别能力,能将伪装目标与背景区分开。     

Harmonic pulsed excitation and motion detection of a vibrating reflective target

Elasticity imaging is an emerging medical imaging modality. Methods involving acoustic radiation force excitation and pulse-echo ultrasound motion detection have been investigated to assess the mechanical response of tissue. In this work new methods for dynamic radiation force excitation and motion detection are presented. The theory and model for harmonic motion detection of a vibrating reflective target are presented. The model incorporates processing of radio frequency data acquired using pulse-echo ultrasound to measure harmonic motion with amplitudes ranging from 100 to 10,000 nm. A numerical study was performed to assess the effects of different parameters on the accuracy and precision of displacement amplitude and phase estimation and showed how estimation errors could be minimized. Harmonic pulsed excitation is introduced as a multifrequency radiation force excitation method that utilizes ultrasound tonebursts repeated at a rate f(r). The radiation force, consisting of frequency components at multiples of f(r), is generated using 3.0 MHz ultrasound, and motion detection is performed simultaneously with 9.0 MHz pulse-echo ultrasound. A parameterized experimental analysis showed that displacement can be measured with small errors for motion with amplitudes as low as 100 nm. The parameterized numerical and experimental analyses provide insight into how to optimize acquisition parameters to minimize measurement errors.     

基于光纤3×3耦合器干涉仪及相位跟踪的振动测量系统

研究了基于光纤3×3耦合器迈克尔逊干涉仪及反馈跟踪相位变化的振动测量系统。该测量系统包含两个反馈控制环节:一个反馈控制环节用于补偿由于环境干扰引起的相位随机漂移;另一个反馈控制环节用于跟踪由于振动引起的相位变化,从而实现对振动幅值及振动方向的测量。该系统可对频率为1.5~200Hz的振动进行测量,测量分辨率可达到10nm。     

膜迷路积水对豚鼠听觉外周系统振动特性的影响

为探究梅尼埃病引起的膜迷路积水对豚鼠听觉系统振动特性的作用机制,通过药物注射建立了内耳膜迷路积水豚鼠模型模拟梅尼埃病病理,搭建了多普勒激光测振系统对健康和膜迷路积水豚鼠听觉系统的振动特性进行测试研究,得到了健康与膜迷路积水豚鼠的听觉系统振动特性,并通过对比明确了内耳膜迷路积水对豚鼠听觉系统振动特性的影响。实验结果表明,在测试频率范围内,离体豚鼠镫骨及圆窗膜的振动特性与活体豚鼠无明显差异,离体豚鼠听觉系统振动特性与输入声压无关,镫骨及圆窗膜的振动位移与输入声压具有明显的线性关系。膜迷路积水显著降低了豚鼠听觉系统镫骨及圆窗膜的振动幅度,在低频及高频区间尤为明显,在500 Hz处镫骨最高由11.64 nm降低至2.27 nm,圆窗膜由24.97 nm降低至5.05 nm。在10 kHz处,圆窗膜最高由0.45 nm降低至0.03 nm。同时膜迷路积水导致豚鼠耳蜗传递比普遍下降,最高在1 kHz和10 kHz处分别由2.82,2.91下降至1.46,0.28。     

磁控溅射沉积薄膜预溅射时间的光谱诊断

利用Omni-λ300系列光栅光谱仪、CCD数据采集和处理系统以及光纤导光系统等构成的等离子体光谱分析系统,实现了实时获取射频磁控溅射过程中等离子体光谱,分别对NiTa,TiAl陶瓷靶,NiAl,TiAl合金靶四种靶材的磁控溅射过程产生的等离子体进行监测,以TaⅡ333.991 nm,NiⅠ362.473 nm,AlⅠ396.153 nm和TiⅠ398.176 nm为分析线,获得了分析谱线强度随时间的变化规律,并以此为依据确定了预溅射时间,同时研究了不同溅射功率和压强对预溅射时间的影响。