医用红外测温仪

医用红外测温仪及温度补偿技术的研究摘要红外测温是目前最主要的非接触式测温方式之一。它具有响应速度快、测量范围宽、灵敏度高等优点，因而被广泛应用于各行各业。红外测温仪在用于体温检测时其测量温度范围应在24.0℃到45.0℃之间，精度要求为±0.1℃。但目前使用的红外测温仪即使其精确度指标为1%，也远远达不到测量体温的精度要求。另外，在24.0℃到45.0℃的温度范围内，红外测温仪的测量精度很容易受外界环境温度的影响，导致其测量误差增大。同时红外测温仪的精度和稳定性很容易受到外界环境温度的影响。因此，减小外界环境因素对红外测温仪的影响具有十分重要的意义。本设计针对目前医用红外测温仪的现状，在查阅了大量国内外文献的基础上，提出了一种新的环境温度的补偿方法。这种方法是根据热释电探测器的工作原理，以及被测物体与环境温度的差值作为参考量，根据其差值的大小确定补偿量的多少。通过数字测温芯片测量环境温度，采用软件补偿的方式，避免了以往用热敏电阻的缺点。在红外测温系统中，红外信号经过光学系统的汇聚、斩波器的调制和热释电探测器的接收后转变成频率为20Hz的脉冲信号。此信号经过放大、滤波、整形和A/D转换成数字信号，再送到单片机中进行数据的处理、补偿和显示。在系统的设计过程中，采用Wave6000单片机仿真系统对单片机进行调试。为了保持各部分之间正确的时序关系，软件全部采用汇编语言来编写。系统经过定标和测试表明：本系统在测量的精度和稳定性上有所提高。关键词红外测温仪；热释电探测器；发射率；温度补偿；单片机；定标AbstractAsamainwayofnon-contactmeasurement,infraredmeasurementhasmanyadvantages,suchasrapidreaction,widemeasurementrangeandhighsensitivityetc.Therefore,non-contactthermometrycanbeusedinvarietyofspots.Wheninfraredthermometerisusedinmedicine,Therangeofinfraredthermometerisregulatedbetween24.0℃to45.0℃anditsprecisionmustbe0.1℃whenitisusedinmedicine.Butmostofinfraredthermometercouldn’tachievethisregulation.Meanwhile,inthistemperaturerange,theprecisionofinfraredthermometercanbegreatlyaffectedbyambienttemperature.Theerrorwillincreasedgreatlytoo.Afterlookeduplotsofdataandrealizedthedefectofinfraredthermometerinmedicinalscopes,anewcompensatorywayonenvironmentaltemperatureispresentedinthispaper.Thisnewwaybasesontheprincipleofpyroelectricdetectoranddefinesthequantityofcompensationaccordingtothetemperaturedifferencebetweentargetanditssurrounding.Theambienttemperatureismeasuredbyadigitalchipandprocessedwithsoftware.Thisnewwaycanovercomethedefectofthermalresistance.Afterfocusedbylens,choppedbychopperandreceivedbydetector,infraredsignalistransformedtoelectricsignalwhosefrequencyis20Hzinthisinfraredsystem.Theelectricsignalisprocessed,compensatedanddisplayedinmicro-controllersystemafteritisamplified,filteredandadjustedbycircuit.Duringdesignofthisinfraredsystem,micro-controlisdebuggedwithWave6000simulationsystemandsoftwareiscompiledinassemblylanguagebecauseoftimingrelationbetweeneverypart.Thetestofthisinfraredthermometerindicatesthatprecisionandstabilityhasimprovedalready.Butitcouldn’treachourcountry’sstandardsonmedicinalthermometer.AbstractKeywordsInfraredthermometer;Pyroelectricdetector;Emissivity;Tempera-turecompensation;Micro-controller;Calibration目录摘要······························································IAbstract··························································II第1章绪论·······················································11.1引言························································11.2红外测温仪的分类···········································21.2.1全辐射测温仪············································21.2.2单色测温仪··············································31.2.3比色测温仪··············································41.3发射率和环境因素对红外测温仪的影响··························51.3.1发射率对红外测温仪的影响································51.3.2环境因素对红外测温仪的影响······························61.4医用红外测温仪的现状········································71.5课题的意义和内容············································81.5.1课题的意义···············································81.5.2课题的内容···············································8第2章光学系统和光电转换·········································92.1红外测温仪的光学系统······························92.1.1红外测温仪光学系统特点································92.1.2常用红外光学系统结构····································92.2红外光学系统设计············································122.2.1透镜成像公式·······································132.2.2透镜成像的误差及对策··································142.2.3透镜参数的确定·····································142.3光电转换··················································152.3.1红外探测器的种类······································152.3.2热释电探测器···········································252.4本章小结··············································27第3章电路系统设计···············································283.1红外信号的调制··············································283.1.1斩波器的设计···········································283.1.2斩波器的驱动········································293.2信号的放大和滤波······································323.2.1有源滤波器的设计·······························333.2.2信号的放大和整形································353.3本章小结···············································37第4章数据的采集和显示···········································384.1数据采集·················································384.1.1A/D转换器的选择···································384.1.2ADS7824功能简介········································384.1.3单片机与A/D转换器的接口电路·····························414.2环境温度的检测········································424.2.1DS18B20功能简介······································424.2.21-wire单总线原理·······································434.2.3与单片机的接口电路······································474.3数据的显示·················································474.3.1可编程IO扩展口的设计·································4.3.2数码显示电路············································484.4本章小结···················································49第5章环境温度补偿及系统实验····································50