外文翻译---改进的红外测温传感系统的移动设备.docx

附录AImproved infrared temperature sensing system for mobile devicesAbstractAn infrared (IR) temperature measurement systemconsists of not only a sensor module and electronics, but also an optomechanical system that guides IR radiation onto the sensor. The geometry and emissivity of the parts affects the reading, if the detector sees not only the target but parts of the measuring system itself. In normal industrial applications, the optics is designed so that the surfaces stabilize to the same temperature as the sensor.This allows the error caused by the device temperature to be easily calibrated away. The correction is valid for stationary conditions and usually near the calibration temperature, which is typically at room temperature.However, we show that if the sensor is embedded into a mobile (hand-held) device which has heat sources, such as power electronics, the normal conditions are no longer valid and the calibration fails. In order to improve infrared temperature sensing for mobile devices, the optics concept was studied and detailed design was performed. In addition, the optics performance was modelled and verified by measurement sensor prototyping. A calibration procedure noticing opeaional temperature variations was applied. The repeatabIlIty of the implemented IR temperature sensor using on a correct transferred calibration curve was better than 0.5 C in an operational temperature range from +12.6 to +49.3 C and target range from +10 to +90 C.Introduction Temperature is probably the most measured environmental parameter in the world. The global warming has dramatically increased the need of accurate temperature measurement of the environment. Temperature measurement is also required in numerous industrial and domestic applications. One important example is the temperature control of a microprocessor in a PC. Based on the temperature information produced by a thermistor both the microprocessor and the cooling system operation can be optimally controlled. Temperature control is also typically needed in household appliances, such as refrigerators, coffee makers and electric ovens. In addition, overheating protection is applied in several devices, such as motors and batteries. In consumer electronics, the main application is body thermometers, typically measured from the tympanic membrane in the ear. It is only natural to consider whether temperature sensing, which has such ubiquitous applications andgeneral interest, could be implemented in mobile handheld devices such as mobile phones. ThermIstor-based temperature sensors exist in a variety of products,including wristwatches and also a few mobile phones. However, their performance is highly limited for a simple physical reason. If we put a thermistor inside a mobile device we are able to measure the temperature of a localisd volume within the device case. However, this does not necessarily correlate at all with the real ambient temperature due to two main reasons. Thermal contact from the environment to the thermistor is weak, but thermal contact from the device itself to the thermistor is strong. In addition, mobile device can contain heat sources, such as power electronics, which easily increase the temperature within the device. Naturally, the heating effect is larger close to the heat sources, but heat conduction throughout the device affects all locations within the device. Locating the sensor outside the cover and isolating it from the rest of the device would improve sensor contact to the environment, but complete isolationis practically impossible to achieve. In addition, a sensor that locates outside the cover will still be vulnerable to heating from the users hand.An alternative principle to implement a well performing environmental temperature measurement in mobile device application is infrared (IR) temperature sensing. IR sensing offers a non-contact method to measure temperature of targets due to the fact that all objects, which temperature is above absolute zero emit IR radiation. The target temperature sensing is based on the measurement of the emitted IR radiation from the object. The main advantages compared to thermistor based measurement are as follows. Thermal signal from the target can be amplified by optics and thermal signal from the device itself can be attenuated by an advantageous optical design and implementation.IR temperature sensingInfrared sensing is based on the fact that the intensity of infrared radiation emitted by a surface depends on its emperature, in the first approximation following Boltzmanns law. Since the field of view of the sensor has to be restricted in a practical mobile application the sensor also sees a surface which typically is not at the same temperature as the surface to be measured. In dealized conditions, this Narcissus effect can be calibrated away using an internal compensation circuit hat measures the temperature of the sensor element itself. A traditional optomechanical design for IR sensing, showing the Narcissus effect is shown in Fig. 1.Fig. 1. Traditional optomechanical design for IR sensing, showing the Narcissus effectAs one can see from Fig. 1 the tube is dominating the optical signal value seen by the detector, if the can is excluded as a commercial component. It is also important to notice that the lens used in the measurement system is producing an optical signal of a same order than the measurement target itself. This is due to the fact that lens material is not totally transparent, but it has absorption at the measurement band, which corresponds to the lens emittance at the equal band.The traditional method rests on two basic assumptions. The measuring device is in practice assumed to be stabilized (at room temperature), and there are assumed to be no internal sources of heat. The situation is very different, however, when the device operational temperature fluctuates strongly due to environmental temperature variation and/or internal heating. In a first approximation to measure the target temperature by its radiated IR power, the total radiance of an object depends on its emissivity and its temperature in whichW= total radiance of the object (W/srxm2)= emissivity Stefan-Bolzmann constantT = absolute temperature of the objectThe incident power is measured by the infrared detector. If the .emissivity of the target is known, the measurement should be quite accurate. Most natural objects have emissivities which are close to 0.95, and this value appears to be set as the default emissivity in all known commercial devices.It is important to notice from the equation 2 that the sensor temperature is typically assumed to be in ambient temperature or at least near to ambient temperature. Intypical mobile application use this assumption, however, is not valid. The factor K includes the view angle or field-of-view (FOV) of the thermopile instrument. In order to obtain an improved spatial resolution at the target, it is necessary to restrict the field of view of the thermopile detector. Traditionally, this is done with a metal tube that has been painted black. The metal conducts heat quite quickly, and in normal circumstances quickly attains a constant temperature throughout the device.The target temperature is possible to determine through calibration, when the Ts is known. In most cases, Ts is measured at the sensor element, with the assumption that the sensor element corresponds well to the temperature of the whole optical system. In equilibrium conditions, the target temperature can thus be calculated by compensating with the measured sensor temperature.Measurements and modeling with traditional opticsWe tested some commercially available IR temperature sensors in actual use cases. Especially we wanted to see performance of the sensors in dynamic operational temperatures. In Table 1 performance of a traditional IR temperature sensor with heated optics is shown. Traditional sensor optical structure consisted of a blackened metal tube and a Fresnel lens made of IR transmitting polymer locating at the tube head. The Fresnel lens collects IR light from target and aims it to the thermopile detector located at the end of the tube.One can see from Table 1 that substantial difference between measurement reading and target reference value was noticed, when the lens was heated above the operational temperature of the system. A smaller error was also noticed, when the system operational temperature was OC, which was 25 degrees below the definedTable 1. Performance of traditional IR temperature sensornominal operational temperature of the system. The system operational temperature was equal to the environmental temperature in the measurement. The used target in the measurement was an aluminum plate painted black and located on top of a Peltier element. The reference temperature was measured using a thermistor, which was attached to the target plate by a silicone.Narcissus effect in the commercial temperature sensor was suspected to be the main reason for the substantial measurement error. The Narcissus effect in the commercial system was modelled by ASAP optical simulation software. The purpose of the simulation was to find out how much optical signal is actually from the target compared to optical and mechanical structures of the measurement system. In order to get estimation of the actual emissivity values of the critical optical and optomechanical structures used in the commercial measurement unit, reflectivity (and transmissivity in some cases) of these structures were measured at wide optical band by Biorad Fourier Transform Infrared (FTIR) spectrometer. Average reflectivity (and transmissivity) at 8 . 14 Jlm band were used to deduce the emissivity value in the optical simulations.Designs to improve system performanceNarcissus effect is clearly a very critical characteristic limiting the measurement performance of an IR temperature sensor. In order to improve performance the Narcissus effect has to be minimised by increasing the transmittance of optics and decreasing the relative amount of optical signal from the optomechanics. The field-of-view (FOV) of a Perkin-Elmer thermopile detector model TPS 333 for example is 100 degrees defined at the 50% relative response points. The wide FOV causes that the optomechanics of the measurement system can easily be seen by the detector. Use of reflective optics instead of refractive optics can provide higher optical transmittances through very high reflectivity surfaces. In addition, the reflective optics can be designed in such a way that there are only high reflectivity optical surfaces within the FOV of the detector. The high reflectivity of the surface corresponds to a low emissivity, which means that a low relative optical signal originates from the high reflectivity surface. In practice it is easier to achieve high optical transmittance through reflective optics at 8 to 14 Jlm band than with refractive optics. Gold and aluminium have high reflectivity from 8 to 14 Jlm band. Aluminium is more cost-efficient material than gold and therefore itsuse is advantageous in mobile applications. The average reflectivity of aluminium is over 97% from 8 to 14 Jlm.Reflector system preliminary specifications were as follows. Optics compatible with similar IR detectors used in commercially available sensors, collects light with object diameter to distance ratio of approximately 1:6 and maximum height of 10 mm for the whole optical structure. The nominal FOV for the IR temperature sensor was specified to 10 degrees defined by 50% relative intensity points. A parabolic reflector was designed on top of the TPS 333 thermopile detector to fulfil the FOV requirement. The parabolic shape was chosen because the shape was able to limit the sensor field of view to sufficiently narrow acceptance cone. Compound parabolic concentrator (CPC) and conical surfaces were also considered, but they were not able to limit the FOV adequately. The designed parabolic reflector and its dimensions are shown in Fig. 2.Fig. 2. Designed optical system and its dimensionsThe parabolic reflector surface is 9 mm long. Input aperture diameter is 4.9 mm and output aperture diameter is 1.56 mm. The output aperture is designed in such a way that it does not obscure any rays originating inside the FOV.附录B改进的红外测温传感系统的移动设备摘要一个红外线（ IR ）温度测量系统包括不仅是一个传感器模块和电子产品，而且是光学机械系统，红外辐射导游到传感器。的几何形状和发射率的部分影响阅读，如果探测器将不仅是目标，但部分测量系统本身。在正常的工业应用，光学设计，使表面的稳定，以相同的温度作为传感器。它允许误差所造成的设备温度容易校准了。更正的有效期为固定的条件，通常附近的校准温度，通常是在室温。然而，我们表明，如果传感器嵌入到移动（手持式）装置已热源，如电力电子，在正常情况下不再有效和校准失败。为了提高红外温度感应的移动设备，光学概念进行了研究和详细设计完成。此外，光学性能为蓝本，并验证了测量传感器的原型。校准程序发现操作 1 ional适用于温度变化。重复性的实施红外温度传感器的正确使用校准曲线转移优于 0.5 C的温度范围内由12.6至49.3 C和目标范围从10到90 C。绪言在世界环境中温度可能是最常测量环境参数。全球变暖显着增加，需要准确的温度测量的环境。温度测量，也需要在许多工业和家庭应用。一个重要的例子是温度控制的微处理器的PC 。基于温度资料所生产的热敏电阻的微处理器和冷却系统，可最优化控制。温度控制也通常需要在家用电器，如冰箱，咖啡壶和电烤炉。此外，过热保护，适用于一些设备，如汽车和电池。在消费电子产品，主要应用是身体温度计，通常测量鼓膜在耳。这是很自然，以考虑是否温度传感，它这种无处不在的应用和普遍关心的，可在移动手持设备，如手机。热敏电阻的温度传感器存在于各种产品，包括手表，也有少数手机。然而，他们的业绩是非常有限的一个简单的物理原因。如果我们把热敏电阻内的移动设备，我们能够测量温度在某物体体积内的设备情况。然而，这并不一定在所有相关的实际环境温度由于主要有两个原因。接触热的环境，热敏薄弱，但接触的设备本身的热敏电阻是坚定的。此外，移动设备可以包含热源，如电力电子技术，可以轻松增加温度范围内的设备。当然，热效应是较大的接近热源，但热传导影响整个装置内所有地点的设备。定位传感器以外的覆盖面和孤立它的其余部分设备将改善传感器接触的环境，但完全孤立实际上是不可能实现的。此外，传感器位于外覆盖仍将是脆弱的暖气从用户的手。另一种原则来执行表现良好环境温度测量中的应用是移动设备的红外（ IR ）温度传感。红外遥感提供了非接触式温度测量方法的目标，原因是所有的物体，温度高于绝对零度发出红外辐射。目标温度传感是基于测量的红外辐射排放的对象。的主要优点相比，热敏电阻测量如下。热信号，目标可以放大的光学和热信号装置本身可以减弱有利的光学设计和实施。红外温度传感红外传感是基于这样一个事实，即红外辐射强度所发出取决于它的表面温度，在第一近似值以下波尔兹曼的规律。自视场传感器已受到限制，在实际的移动应用的传感器还看到了表面通常不是在相同温度下的表面来衡量。在可处理的条件，这水仙效果可校准以外使用内部补偿电路措施的温度传感器元件本身。传统的光学机械设计，红外传感显示了水仙效果如图1所示。图1 传统的光学机械设计，红外传感，显示了水仙的效果我们可以从图1看到，占据了光信号的价值被检测的管道，如果不能被排除作为一个组成部分。同样重要的是，请注意，所用的镜头在测量系统产生光信号的顺序比测量目标本身。这是由于这样一个事实，即透镜材料不完全透明的，但它吸收的测量带，相当于镜头发射在平等波段。传统方法有两个基本假设。该测量装置是在实践中被假定为稳定（在室温条件下） ，有被假定为没有内部热源。情况是非常不同的，然而，当设备工作温度波动强烈由于环境温度变化和/或内部加热。在第一近似值来衡量的目标温度的红外辐射功率，总辐射的对象取决于其辐射和温度，其中：为材料表面发射率。 ，为 Stefan-Boltzmann常数。