计算机模拟双折射滤光片抑制绿激光器噪声

结合Nd:YVO4激光器自身的特点及双折射滤光片的选波长作用,提出以控制晶体的厚度及光轴的夹角来实现单模振荡.经计算机模拟,分析其滤波效果,证明用双折射滤光片解决"绿光问题"是可行的.YVO4和KTP晶体的厚度分别为d1=0.532mm,d2=4.457mm;调谐角分别为13.3°、27.0°.     

计算机模拟双折射滤光片抑制绿激光器噪声

结合 Nd:YVO4 激光器自身的特点及双折射滤光片的选波长作用 ,提出以控制晶体的厚度及光轴的夹角来实现单模振荡。经计算机模拟 ,分析其滤波效果 ,证明用双折射滤光片解决“绿光问题”是可行的。 YVO4 和 KTP晶体的厚度分别为 d1 =0 .5 3 2 mm,d2 =4.45 7mm;调谐角分别为 1 3 .3°、2 7.0°。     

噪声抑制技术在数据采集系统中的应用

阐述了在实用智能化机械量测试分析仪数据采集系统中所采取的一系列有效的抗干扰措施,有效地抑制了其数据采集输入信号的噪声.     

浅谈汽车交流发电机噪声及其抑制

随着汽车工业的迅速发展与竞争环境的变化,汽车交流发电机的噪音问题已经越来越引起各交流发电机制造厂家的重视。从噪声产生的3个方面（即电磁噪声、通风噪声、机械噪声）,叙述了噪声的形成原因,并提出了改善噪声的一些措施。     

传感器应用中噪声的产生及其抑制方法

在智能化控制系统中，传感器是用来感知、测定各种变化量的重要器件，在其使用中的噪声直接影响着智能化控制的效果。针对传感器在应用中噪声的产生、表现形式、耦合方式进行了较详细的论述。对传感器回路的噪声抑制应考虑到：除去回路系统内有噪声源；回路设计时应采用平衡方式；电路布置时不要形成环路；避免随意接地；线路布线应采用绞合线；恰当地使用屏蔽线，对高频噪声宜采用薄金属屏蔽层的屏蔽线，在低频噪声时或磁场干扰较强的情况下，宜采用较厚金属屏蔽层的屏蔽线；应用时还应充分考虑传感器的特性，尤其是阻抗、信号电平等因素。     

超声无损检测中的缺陷识别与噪声抑制

在传统的小波信号处理器基础上,根据解析小波变换能准确提取信号相位的特性,利用超声检测信号的相位信息,提出一种新的多缺陷识别与噪声抑制算法。该算法充分运用超声信号的时域、频率和相位信息,能检测多个具有不同频谱特性的缺陷。实验结果表明该算法不仅消噪性能好,而且提高了缺陷的纵向分辨率。     

风机噪声预测,抑制及显示的新思路

对声压法、声强法测量进行了评估,提出用声强法进行风机噪声源诊断及风机噪声的预测、抑制的新思路,并给出测量方法,对误差进行了分析,同时提出了改进措施。     

V型腔激光器倍频晶体长度分析和实验研究

根据倍频光转换效率公式和腔内倍频的稳态条件,推导倍频光功率密度的最大值和最佳倍频晶体长度的表达式,计算了当腔内损耗为5%,以Nd:YVO4和Nd:YAG为激光晶体时KTP晶体的最佳长度,分别采用Nd:YAG和Nd:YVO4为激光晶体进行实验。在Nd:YVO4/10mmKTP实验中,当泵浦光为15W时,获得了2.67W绿光输出,光-光转换效率达17.8%。     

Formation of variable-spatial frequency interference patterns with the use of birefringent crystal prisms for laser Fourier spectroscopy

Splitting of orthogonally polarized radiation components at the exit of birefringent crystal prisms (BCPs) having a special structure and fabricated from uniaxial Iceland spar crystals is studied by the vector analysis method. For these prisms, the angle of splitting between the ordinary (o) and extraordinary (e) beams at the BCP exit depends linearly on the angle of incidence of a collimated laser beam onto the BCP entrance face. This dependence has the maximum slope only for two fixed orientations of the optical axis vectors a ₁ and a ₂ in both crystal wedges (BCP components). As a result of interference of polarized o- and e-waves, a straight-line interference pattern with a controlled and smoothly changed spatial frequency in the range from 0 to 125 periods/mm can be formed directly at the BCP exit. The BCP ability to form a sinusoidal interference pattern with the modulation depth not lower than 30% and with a varied spatial frequency at the aperture up to 30 mm makes it possible to use the BCP as a basis for creating a compact static Fourier spectrometer with the ultimate theoretical resolution λ/Δλ up to ∼2000.     

双块KTP晶体正交倍频的绿光激光器特性研究

基于非线性光学的频率变换理论,采用双块磷酸氧钛钾(KTP)晶体外腔正交倍频的方式产生二次谐波以提高基频光的倍频转换效率。用长度分别为6mm,8mm,15mm的三块KTP晶体进行实验,比较了双块KTP晶体正交和平行串接以及单块KTP晶体的倍频特性,得到几组倍频转换效率随基频光功率密度变化的曲线。实验结果表明,采用双块KTP晶体倍频的倍频激光器能够有效地提高绿光激光器的动态范围且在520～750MW/cm2,双块KTP晶体正交串接倍频比长度是两块晶体之和的单块长KTP晶体的倍频转换效率高近30%。     

计算机微视觉微运动测量系统图像噪声分析

对计算机微视觉微运动测量系统采集的图像噪声及处理方法进行了研究.分析了各种在微运动测量时引起测量误差的图像噪声.在此基础上,通过对一幅典型的由计算机微视觉微运动测量系统采集的MEMS图像进行分析,给出了减少这些噪声的常用方法.分析表明了对于这种微结构图像以下噪声处理方法的有效性:首先采用中值滤波器减少散粒噪声以及采用一个低通滤波器减少高频噪声,然后采用两点修正法可以减少固定图像噪声;此外,在采集图像时适当增加曝光时间可以减少机械噪声的影响.     

Pulsed laser noise analysis and pump-probe signal detection with a data acquisition card

A photodiode and data acquisition card whose sampling clock is synchronized to the repetition rate of a laser are used to measure the energy of each laser pulse. Simple analysis of the data yields the noise spectrum from very low frequencies up to half the repetition rate and quantifies the pulse energy distribution. When two photodiodes for balanced detection are used in combination with an optical modulator, the technique is capable of detecting very weak pump-probe signals (ΔI/I(0) ~ 10(-5) at 1 kHz), with a sensitivity that is competitive with a lock-in amplifier. Detection with the data acquisition card is versatile and offers many advantages including full quantification of noise during each stage of signal processing, arbitrary digital filtering in silico after data collection is complete, direct readout of percent signal modulation, and easy adaptation for fast scanning of delay between pump and probe.     

Acquisition of low-frequency signals immersed in noise by random sampling and finite impulse response filters

This article presents a method for digital acquisition of low-frequency signals immersed in high-frequency noise when noise frequency is higher than the sampling one. This method uses no antialiasing filters, but random sampling and filtering instead. Its formulation is developed for JRS (jitter random sampling) and finite impulse response (FIR) filters. The proposed method is experimentally tested on three FIR filters: moving average, windowed linear phase, and constrained least square.     

声强法噪声测量微机控制系统的设计与实现

用声强技术对机床用减速箱的噪声识别,设计了一个以单片机系统为核心的声功率谱测量分析仪,以便能使噪声测量与其它参数测量融为一体,完成机床用减速箱的综合测试台的设计。     

液力自动变速器原理模拟屏的微机控制

介绍了单片机控制的汽车自动变速器原理模拟屏,给出了模拟屏的控制原理和方法,论述了系统的接口驱动电路软件设计。实际使用表明,系统具有功能强、方便操作的特点,使用效果很好。     

Influence of measurement noise and laser arrangement on measurement uncertainty of laser tracker multilateration in machine tool volumetric verification

This paper aims to present different techniques and factors that affect the measurement accuracy of a commercial laser tracker responsible for capturing checkpoints used in machine tool volumetric verification. This study was conducted to uncover various sources of error affecting the measurement uncertainty of the laser tracker, additional sources of error that further contributed to the uncertainty, and the factors influencing these techniques. We also define several noise reduction techniques for the measurements.The improvement in the accuracy of captured points focuses on a multilateration technique and its various resolution methods both analytically and geometrically. Similarly, we present trilateration and least squares techniques that can be used for laser tracker self-calibration, which is an essential parameter in multilateration.This paper presents the influence of the spatial distribution of laser trackers (LTs) in measurement noise reduction by multilateration, which produces an improvement in volumetric error machine tool reduction. A study of the spatial angle between LTs, the distance and the visibility of the point to be measured are presented using a synthetic test. All of these factors limit the scope of multilateration. Similarly, a comparison of self-calibration techniques using the least squares and trilateration methods with which to determine the relative position of the laser tracker employees is presented. We also present the influence of the relationship between the radial and angular measurement noise self-calibration processes as it relates to the volumetric error reduction achieved by the machine tool with multilateration. All studies were performed using synthetic tests generated using a synthetic data parametric generator.