JD-3型数字式照度计

该照度计采用3~(1/2)位A/D转换器进行A/D转换,并配以液晶显示器显示读数,显示数据清晰、稳定。该照度计全部采用国产元器件,运用了高性能的运算放大器,提高了测试精度。还介绍了仪器的主要技术指标和工作原理。图4。     

单片微型计算机的A/D转换接口技术

本文探讨了用D/A转换器加比较器(OP)的条件下,用软件实现A/D转换的方法,以及用带I2C总线接口的A/D转换芯片PCF8591的A/D转换接口技术.     

高速低功耗转换器集成电路

日本夏普公司最近研制出两种片状元件是8位的双极A/D转换器和D/A转换器。这两种产品由于     

基于单片机的模数转换接口设计

随着数字处理技术的发展,模拟/数字转换(A/D转换器)在数据采集系统中的应用越来越广泛.通过对A/D转换原理的介绍,绐出了以AT89C51单片机为核心控制芯片,通过对MAX197模数转换芯片的控制进行数据采集的接口电路和程序流程,为设计数据采集系统提供了一种方案.     

8098单片机热电阻测温系统

本文叙述了8098单片机内四输入10位A/D转换器的工作原理、使用方法。讨论了在智能流量计中以8098中A/D转换器进行温度测量时应考虑的问题。     

基于DSP与PCI总线的电表校验装置的设计

本文叙述在进行电量测量装置的高速高精度校验中．采用DSP（TMS320VC5402)．PCI接口芯片(PCI9054)、高精度A/D转换器等接口电路的实现方法．     

基于DSP的音频信号采集和处理设计

介绍基于TMS320C5402的音频信号采集和处理系统的设计方法,实现模/数(A/D)数/模(D/A)转换电路设计,论述如何利用TMS320C5402的多通道缓冲同步串口(McBSP)CS5360和DAC1220芯片接口来实现音频信号的采集和输出方案.     

基于DSP的音频信号采集和处理设计

介绍基于TMS320C5402的音频信号采集和处理系统的设计方法,实现模/数(A/D)数/模(D/A)转换电路设计,论述如何利用TMS320C5402的多通道缓冲同步串口(McBSP)CS5360和DAC1220芯片接口来实现音频信号的采集和输出方案.     

交流电压真有效值的简便数字式测量

介绍由有效值变换器AD736、A/D转换器7106和液晶显示器LD-B7015A组成的交流电压真有效值测量电路。     

气相色谱仪温控系统A／D和D／A转换技术的应用

在许多大型精密仪器和设备中,配有不同结构的温度控制和测量系统。这些温控和测量系统的精度是仪器和设备重要指标。而温控和测量精度在很大程度上是取决于A/D(模数转换)和D/A(数模转换)的转换精度。因此A/D和D/A转换在以数字为控制基础的各种仪器装置上是至关重要的环节。下面仅就飞利浦公司(PHILIPS)气相色谱仪计算机控温系统TMI(温度监控器)中A/D     

Wide-band acousto-optic deflectors for large field of view two-photon microscope

Acousto-optic deflector (AOD) is an attractive scanner for two-photon microscopy because it can provide fast and versatile laser scanning and does not involve any mechanical movements. However, due to the small scan range of available AOD, the field of view (FOV) of the AOD-based microscope is typically smaller than that of the conventional galvanometer-based microscope. Here, we developed a novel wide-band AOD to enlarge the scan angle. Considering the maximum acceptable acoustic attenuation in the acousto-optic crystal, relatively lower operating frequencies and moderate aperture were adopted. The custom AOD was able to provide 60 MHz 3-dB bandwidth and 80% peak diffraction efficiency at 840 nm wavelength. Based on a pair of such AOD, a large FOV two-photon microscope was built with a FOV up to 418.5 μm (40× objective). The spatiotemporal dispersion was compensated simultaneously with a single custom-made prism. By means of dynamic power modulation, the variation of laser intensity within the FOV was reduced below 5%. The lateral and axial resolution of the system were 0.58-2.12 μm and 2.17-3.07 μm, respectively. Pollen grain images acquired by this system were presented to demonstrate the imaging capability at different positions across the entire FOV.     

基于线性神经网络的高速光偏振仪

提出了一种新型的高速光偏振仪。使用一个既能产生反射光衍射又能产生透射光衍射的特殊金属光栅作为分光器,将入射光分为多束。利用光电探测器将其中的四束1级衍射光的光强线性地转换为电信号,将它们作为神经网络的输入,入射光Stokes参数作为神经网络的输出,建立多层线性神经网络模型。通过网络训练,得到电信号与入射光Stokes参数之间的映射关系。测出电信号后,通过训练后的网络可以计算出入射光待测的Stokes参数。测试结果表明:工作波长为632.8 nm时,Stokes参数测量值与理论值的平均偏差小于2%。该仪器结构紧凑、易于安装,具有测量速度快、精度高和非破坏性等优点。     

基于Sagnac的分布式光纤传感声学传感器

介绍了一种基于Sagnac的分布式光纤声学传感器. 这种声学传感器通过光电探测器、 数据采集卡、 滤波器和音频放大将3×3耦合器处干涉的光信号转换为电信号且实现音频信号的还原. 为了研究此分布式光纤声学传感器的性能, 分析了基于零频点实验声源扰动定位的原理, 并运用快速傅立叶变换将时域信号转化为频域信号显示声源扰动产生的零频点. 实验结果表明, 基于Sagnac的分布式光纤声学传感系统可以很好地实现声音信号的还原和定位.     

程序控制调光在新型航空相机中的应用

为了在地面景物亮度变化大时获取正确曝光的航空图像,新型航空相机需要设计宽范围的调光控制系统。提出了一种光圈和快门速度都可以自动调节的宽范围程序控制调光模式,介绍了程序控制调光的设计原理和系统组成,给出了系统的硬件电路和软件流程设计,经测试和使用证明,该系统适应调光范围大,控制精度高,工作稳定可靠,满足了航空摄影侦察的要求。     

AOD精炼高强度低合金钢工艺及应用

从AOD工作层砌筑与烘烤、电弧炉熔炼配合、AOD精炼操作过程控制及产品验证等方面进行阐述,证明用AOD与电弧炉双联精炼高强度低合金钢工艺切实可行.     

全光波长转换实验研究

对基于光纤光栅外腔半导体激光器增益饱和效应的全光波长转换器的静态与动态特性进行了实验研究。为消除反馈光与转换信号输出光对光源的不利影响及提高光输入、输出信号耦合效率,提出了采用环形器进行信号耦合的光学结构。进行了155MB/s信号的动态波长转换实验。     

High temporal and spatial resolution studies of bone cells using real-time confocal reflection microscopy

Chick and rat bone-derived cells were mounted in sealed coverslip-covered chambers; individual osteoclasts (but also osteoblasts) were selected and studied at 37°C using three different types of high-speed scanning confocal microscopes: (1) A Noran Tandem Scanning Microscope (TSM) was used with a low light level, cooled CCD camera for image transfer to a Noran TN8502 frame store-based image analysing computer to make time lapse movie sequences using 0.1 s exposure periods, thus losing some of the advantage of the high frame rate of the TSM. Rapid focus adjustment using computer controlled piezo drivers permitted two or more focus planes to be imaged sequentially: thus (with additional light-source shuttering) the reflection confocal image could be alternated with the phase contrast image at a different focus. Individual cells were followed for up to 5 days, suggesting no significant irradiation problem. (2) Exceptional temporal and spatial resolution is available in video rate laser confocal scanning microscopes (VRCSLMs). We used the Noran Odyssey unitary beam VRCSLM with an argon ion laser at 488 nm and acousto-optic deflection (AOD) on the line axis: this instrument is truly and adjustably confocal in the reflection mode. (3) We also used the Lasertec 1LM11 line scan instrument, with an He-Ne laser at 633 nm, and AOD for the frame scan. We discuss the technical problems and merits of the different approaches. The VRCSLMs documented rapid, real-time oscillatory motion: all the methods used show rapid net movement of organelles within bone cells. The interference reflection mode gives particularly strong contrasts in confocal instruments. Phase contrast and other interference methods used in the microscopy of living cells can be used simultaneously in the TSM.     

基于嵌入式Linux的温度测量系统

设计了一种基于嵌入式Linux的比色测温系统,硬件部分基于ARM9系列S3C2410处理器,软件部分采用Linux最小系统的设计。采用光纤传输被测物体发射的光信号,用光纤光栅实现单波长信号获取,经信号处理,表征被测温度可以是亮度式、比色式、多色式信号。应用黑体炉及亮度灯对研制的仪器标定。标定及试验验证结果表明:系统测温重复性<2℃,系统的测量误差<0.5%。     

秸秆燃烧和沙尘对气溶胶光学特性的影响

利用多年积累的我国几个典型地区的太阳辐射计观测数据,反演了秸秆燃烧和沙尘日及其前后晴朗日的气溶胶光学厚度(AOD)和表征粒子尺度的ngstrm指数(α),并运用观测结果和反演数据对已知气溶胶源予以验证。对比分析了多个典型地区源自秸秆燃烧和沙尘的气溶胶光学特性,结果显示,秸秆燃烧和扬尘时AOD都大幅增加,而α在秸秆燃烧时比通常晴朗日增大,取值大于1.3;在扬尘时比通常晴朗日明显减小,取值小于0.5。另外,不同地区不同气溶胶源的AOD与α的关系明显不同。分析结果表明,α可作为秸秆燃烧和沙尘天气的一个标志参数,为生物燃烧性有机碳黑气溶胶光学特性的检测方法提供依据,也可为分析我国西北城市地区受周边沙漠的影响程度提供有益参考。     

Three-dimensional refractive images for laser measurements techniques

A new technology of visualization and diagnostics of transparent media with gradient inhomogeneities is described. This technology is called three-dimensional laser diffractometry; it is based on refraction of spatially structured laser radiation and digital recording and processing of two-dimensional (in transmitted light) or three-dimensional (in scattered light) refractive patterns. Results of computer simulations of three-dimensional refractive patterns (3D refractograms) for spherically and plane layered media are presented. A setup for observation of 3D refractograms in scattered light is schematically described, the method of obtaining refractograms from experimental two-dimensional refractive patterns is presented, and examples of computer processing of experimental data are given.