光纤气体传感器解调系统软件研究

利用气体分子的吸收光谱,采用分布反馈式半导体激光器(DFB LD)作为光源,使用拓普公司数据采集卡PCI-10016,研究了一种基于计算机的光纤气体传感器谐波检测的实验室解调方案,设计了解调软件进行信号解调,实现了气体体积分数的谐波检测,并能实时显示采集波形及分析波形,检测分辨力可达30×10-6,有很大的实用价值.     

基于单片机的主动激光频率控制技术

为了提高激光器频率的稳定性,提出了用气体吸收效应实现激光器频率误差信号的检测、由单片机进行信号处理的光电控制系统实现主动激光频率稳定;选用89C51单片计算机作为控制系统核心,由软件完成数字滤波、相位检测及频率偏移量计算;通过高压放大器调整激光谐振腔长度,使得频率漂移得到补偿,系统实现闭环控制;采用该主动控制系统的激光器频率长期稳定度优于10^-9,可为精密激光制导武器及精密激光测量技术提供频率稳定的发射光源。     

气体传感器中半导体激光器的温度控制

不同气体分子由于其特征结构不同,对应于不同的吸收光谱,通过气体对特定波长光的吸收,形成了光谱吸收式气体传感器。在光谱吸收式气体浓度检测系统中,保证半导体激光器输出光波长的稳定性是最为重要的,而激光器的温度是影响输出波长的主要因素之一。目前,通常采用激光器内部的热敏电阻器作为激光器温度的测量依据,但受到激光器结构的限制热敏电阻器不能精确快速地指示激光器的温度,影响了检测系统的正常工作。为了解决这个问题,通过对垂直腔面发射半导体激光器应用的分析,在原有热敏电阻器的基础之上,加入对激光器输出波长的监测,形成了热敏电阻器与输出波长的双重检测的温度控制方案,改变传统的仅有热敏电阻器单参数的温度控制方案,形成双参数的数字PID控制决策,实验结果表明:光源温度偏差可以控制在0.01℃以内,进一步提高了光学气体传感器的工作稳定度。     

基于谐波检测技术的光纤甲烷气体传感器的研究

基于甲烷气体的近红外吸收光谱，研究了一种高灵敏度光谱吸收型光纤甲烷气体传感器。采用DFBLD作为光源，通过光源调制实现气体浓度的谐波检测，利用二次谐波与一次谐波的比值来消除由光源的不稳定和变化所引起的检测误差。建立了谐波检测的数学模型，给出了甲烷气体的测量结果。     

基于光谱吸收的光纤水分传感器研究

基于分子的近红外光谱吸收机理,研究一种可以检测水分含量的光纤传感器。对半导体激光器(LD)进行正弦波调制,建立人工神经网络的数学模型,利用NI数据采集卡和神经网络数据拟合实现分子的检测。系统采用双光路结构有效消除了光源光强噪声干扰和光电器件的零点漂移。实验结果表明:传感器性能稳定,灵敏度高,重复性好,并且不受其它气体或杂质的干扰。     

差动吸收式光纤气体传感器研究

本文基于甲烷和乙炔气体的光谱吸收特性,设计了一种差动吸收式光纤气体监测仪。根据被测气体的吸收峰值波长选择LED作为光源。采用不同频率的光源驱动电路实现多种气体浓度的同时检测。为保证测量精度,采用测量信号与参考信号的比值作为输出信号,以及相敏检测技术。对甲烷和乙炔气体浓度的检测实验表明,该系统具有较好的检测灵敏度和测量精度。该系统稍加改变结构参数,也可测量其它气体的浓度。     

吸收式光纤气体传感器的研究

提出了一种通过波长扫描来检测C2H4 和H2S混合气体的体积分数的新方法。采用超发光二极管作为光源, 2个检测通道共用 1根光纤,通过光源调制实现气体的体积分数的谐波检测技术。该系统最小可探测气体的体积分数约为 10-4, 移植性好,对大多数气体均适用。     

新型光纤乙炔气体传感器的研究

基于乙炔的近红外吸收机理,针对采用宽带光源直接进行吸收检测灵敏度不高的缺点,应用宽带光源和梳状滤波器(Fabry-Perot腔)来获得与乙炔气体梳状吸收峰相适应的出射光,来实现乙炔气体浓度的谐波检测,使由于气体吸收而引起的相对输出光功率变化大大提高,检测效率得到改善.建立了谐波检测的数学模型,利用光纤作为传输媒质,实现了在线遥测,提高了测量灵敏度.     

基于可调谐激光光谱的气体传感系统的研究

为了准确快速的检测气体浓度,基于可调谐激光吸收光谱法,设计了一套气体传感系统.研制了带有光纤准直的透射式光学传感气室,采用半导体激光器作为光源,气体的吸收光谱信号由光电探测器接收,经锁相放大器检测出谐波信号,用二次谐波和一次谐波的比值来获得气体的浓度,消除了光强波动、粉尘及视窗污染的影响.实验表明,二次谐波和一次谐波的比值与气体浓度值之间的线性相关度可达0.9944,可以准确获得气体的浓度信息.     

光谱吸收型光纤气体传感器的研究

研究和讨论了一种易于实现的光谱吸收型光纤气体传感器.采用LED作为光源,利用可调谐法布里-珀罗腔的选频特性进行检波,并采用谐波检测,显著提高了检测的灵敏度.同时,采用多光路设计和软件控制相结合,可在线检测多种气体,克服了以往气体传感器只能检测一种气体的缺点,大大增加了该传感器的适用性.     

手指静脉识别传感器的光源设计

针对手指静脉图像采集系统中近红外LED光源的光强均匀性相对较差的问题,设计了一种等边三角形结构的光源阵列.通过应用近红外LED光源的数学模型和斯派罗法则优化两个相邻光源的距离,确定了两颗光源之间的最优距离为6.26 mm,对该光源阵列进行仿真形成面积为10 mm ×20 mm的均匀光照区域.对此光源阵列进行硬件实验,证明等边三角形结构的光源阵列比单排的光源阵列在均匀性和图像质量上更加突出.     

Multi‐primary image projector using programmable spectral light source

This paper presents a practical prototype of a multi‐primary image projector system in which light source spectra can be programmable for suiting any purpose. Our multi‐primary projection system is mainly configured with a light source component and an image projection component. The programmable light source can reproduce any spectral curve. Spatial images are then generated using a digital mirror device chip that quickly controls the intensity of the light source spectra in 2D image plane. The multi‐primary images in our projection system are reproduced by multiplexing the time‐sequential images with different primary colors. Our multi‐primary image projector realizes not only wide gamut projection but also spectral projection. To achieve this, we also show how light source spectra of four or six primary colors are designed.     

纳米级光栅容栅融合测量系统研究

利用容栅测量系统中激励信号源的设计技术,产生一组多相输出的调制信号源,作为光栅测量系统的多相线阵光源激励信号,发出的多相调制光信号,再经过标尺光栅调制后,由光电转换元件接收并获得一个复合的电信号.该信号经处理电路后,可获得一个频率与激励信号源的基波频率相等的电信号,检测这两个信号间的相位差的变化,可得到标尺光栅的移动距离x.将容栅和光栅测量技术有机地结合,并通过提高相位检测电路的细分数和减小线阵光源的点距,可达到亚微米或纳米级的测量分辨力.     

基于参考图像的原子模型渲染方法

伴随着生物学的发展与纳米电子器件仿真技术的进步,原子结构在现代化科技领域发挥至关重要的作用。原子结构的复杂细节使得渲染效果受光源位置影响较大,导致了原子模型渲染工作的困难。基于此,提出了一种基于参考图像的原子模型渲染方法,计算出参考图像的光照参数用于原子模型的渲染。首先,通过改变光源位置,利用POV-Ray脚本实现不同光源角度下的批量模型渲染,采集光源位置参数及渲染图像得到对应光源位置的渲染图像数据集;接着,以残差神经网络为主干设计光源估计网络,并在网络中嵌入注意力机制提升网络准确性,使用优化后的光源估计网络对数据集进行训练,回归光源位置参数;最后将训练好的卷积神经网络应用于参考图像的渲染参数估计中,利用渲染参数渲染目标模型。实验结果显示。通过网络预测的参数与真实照明参数误差极小,具有高度可靠性。     

模型车激光导向的实验模拟

用实验模拟了模型车激光导向的原理。实验系统根据接收到的光信号的强弱,利用PWM改变电机转动的方向和速度,当光源偏离参考位置时,电机转速将变大或变小;当光源越界时,电机将反转。实验模型基本实现了模拟功能。     

Light source position and reflectance estimation from a single view without the distant illumination assumption

Several techniques have been developed for recovering reflectance properties of real surfaces under unknown illumination. However, in most cases, those techniques assume that the light sources are located at infinity, which cannot be applied safely to, for example, reflectance modeling of indoor environments. In this paper, we propose two types of methods to estimate the surface reflectance property of an object, as well as the position of a light source from a single view without the distant illumination assumption, thus relaxing the conditions in the previous methods. Given a real image and a 3D geometric model of an object with specular reflection as inputs, the first method estimates the light source position by fitting to the Lambertian diffuse component, while separating the specular and diffuse components by using an iterative relaxation scheme. Our second method extends that first method by using as input a specular component image, which is acquired by analyzing multiple polarization images taken from a single view, thus removing its constraints on the diffuse reflectance property. This method simultaneously recovers the reflectance properties and the light source positions by optimizing the linearity of a log-transformed Torrance-Sparrow model. By estimating the object's reflectance property and the light source position, we can freely generate synthetic images of the target object under arbitrary lighting conditions with not only source direction modification but also source-surface distance modification. Experimental results show the accuracy of our estimation framework.     

基于PWM的弱视治疗仪光源设计与实现

目前弱视治疗仪一般都采用白炽灯作为光源,利用电阻限流方式控制光强,存在发光效率低,寿命短,发热量高,体积大,可调光强级别较少,光源亮度不稳定等缺陷。针对这些缺陷,文章采用LED设计光源,利用PWM技术控制灯源光强,选择单片机AT89C52为微控制器,通过C51语言编写控制程序,对单片机输出PWM脉冲占空比进行调节,PWM脉冲直接控制驱动电路输出电流的大小,从而达到控制LED亮度强弱的目的,驱动电路的反馈设计确保了输出电流稳定,使LED光源亮度稳定,不易闪烁,比起传统白炽灯对眼睛的伤害减弱。通过实验,结果表明基于PWM技术驱动的LED光源的亮度稳定,并能提供10级以上的光强。     

Error analysis of surface normals determined by radiometry

Surface normals can be computed from three images of a workpiece taken under three distinct lighting conditions without requiring surface continuity. Radiometric methods are susceptible to systematic errors such as: errors in the measurement of light source orientations; mismatched light source irradiance; detector nonlinearity; the presence of specular reflection or shadows; the spatial and spectral distribution of incident light; surface size, material, and microstructure; and the length and properties of the light source to target path. Typically, a 1° error in surface orientation of a Lambertian workpiece is caused by a 1 percent change in image intensity due to variations in incident light intensity or a 1° change in orientation of a collimated light source. Tests on a white nylon sphere indicate that by using modest error prevention and calibration schemes, surface angles off the camera axis can be computed within 5°, except at edge pixels. Equations for the sensitivity of surface normals to major error sources have been derived. Results of surface normal estimation and edge extraction experiments on various non-Lambertian and textured workpieces are also presented.     

Fabrication of UV range light guide plate

The light guide plate, as part of the backlight unit in a cellular phone or liquid crystal display, has evolved to meet market demands for low power consumption, high-luminance and high-quality displays. Along with the advance of the light guide plate, LEDs have undergone development as light source for light guide plates. Surpassing the limitations of LED emission in the visible light range, LEDs that emit UV light have been developed. In recent years, the UV light are used as a source of light of the air cleaner, and it is used as a source of light to activate the titanium oxide which is photocatalyst. But common UV light sources are either line or point light sources. We study surface illuminators that incorporate diffusers in the visible light range. Applying our existing technology, we constructed an unprecedented UV surface illuminator (surface light source) and measured it using a photocatalyst. The experiment results are presented in this report.     

Multiple light source detection

This paper presents the V2R algorithm, a novel method for multiple light source detection using a Lambertian sphere as a calibration object. The algorithm segments the image of the sphere into regions that are each illuminated by a single virtual light and subtracts the virtual lights of adjacent regions to estimate the light source vectors. The algorithm uses all pixels within a region to form a robust estimate of the corresponding virtual light. The circumstances under which the light source detection problem lacks a unique solution are discussed in detail and the way in which the V2R algorithm resolves the ambiguity is explained. The V2R algorithm includes novel procedures for identifying the critical lines that bound the regions, for estimating the light source vectors, and for identifying opposite light pairs. Experiments are performed on synthetic and real images and the performance of the V2R algorithm is compared to that of a recent algorithm from the literature. The experimental results demonstrate that the proposed algorithm is robust and that it gives substantially improved accuracy.