水质色度的色差测量方法

为了适应自动测量水质色度的要求,克服目前水质色度测量方法的局限性,提出了采用色差值测量水质色度的方法。实验建立了色差与色度之间的数值关系,通过测量水样的光谱透射比,计算色差值,就可得到水样色度值。系统经定标后测量过程不需要标准溶液,待测水样的颜色也不再受到限制。实际水样测量表明,测量结果与国家标准方法一致,且灵敏度更高,重复性更好。     

一维高温温度场测试技术

研制了可对一维高温温度场进行测量的扫描式高温计．该扫描式高温计分为旋转扫描式光学系统、比色高温计和上位机三个部分．在分析温度场测量要求的基础上,推导了比色光学高温计的测量原理,建立了数学模型．基于光的反射理论,研究了旋转扫描式光学系统与一维温度场之间的运动关系．利用光学光纤将光学探头接收的光信号进行远距离传输,增加了测量的便利性和整套装置对测量环境的适应能力,专用的微型工控及控制系统提高了这套装置独立工作及与其他设备进行协调合作的能力．对比色高温计的波长函数和测量精度进行了标定,校验结果表明在800℃～3500℃范围内的测量精度为1％．最后,利用扫描式高温计对棒状碳／碳试样的轴向温度场进行了测量,通过几个固定点温度对一维温度场的测量精度进行了校验,最大测量误差为3．09％．     

Temperature estimation of high-power light emitting diode street lamp by a multi-chip analytical solution

Light emitting diodes (LEDs) are now widely used in many fields including traffic lights, vehicle backlights and liquid crystal display (LCD) displays because of their long life, good illumination efficiency and low energy consumption. At present, LEDs are increasingly replacing the traditional lighting and are being used in general illumination such as the street lamp. For the high-power LED street lamps, good light extraction is the most important thing, but low junction temperature of the LED modules is also critical for achieving a long lifetime and a high optical efficiency. Actually, there have been many reports about early failures of street lamps, called dead lamps that have been regarded as a barrier in the public and administration acceptance of LED street lamps. Therefore temperature estimation is always a crucial issue for LED product development. A multi-chip spreading thermal resistance model was applied to estimate the temperature distribution of LED street lamp. The experiment was first done to obtain temperatures of several locations in a prototype LED street lamp. Then the multi-chip spreading resistance model was established to calculate the full temperature distribution. Comparison between the model calculation and experimental measurement showed a good agreement, which demonstrates that the present model can be used in engineering design to estimate the temperature distribution of high-power LED street lamps.     

Measurement of surface temperature and emissivity by a multitemperature method for Fourier-transform infrared spectrometers

Surface temperatures are estimated with high precision based on a multitemperature method for Fourier-transform spectrometers. The method is based on Planck's radiation law and a nonlinear least-squares fitting algorithm applied to two or more spectra at different sample temperatures and a single measurement at a known sample temperature, for example, at ambient temperature. The temperature of the sample surface can be measured rather easily at ambient temperature. The spectrum at ambient temperature is used to eliminate background effects from spectra as measured at other surface temperatures. The temperatures of the sample are found in a single calculation from the measured spectra independently of the response function of the instrument and the emissivity of the sample. The spectral emissivity of a sample can be measured if the instrument is calibrated against a blackbody source. Temperatures of blackbody sources are estimated with an uncertainty of 0.2-2 K. The method is demonstrated for measuring the spectral emissivity of a brass specimen and an oxidized nickel specimen.     

A New Measurement Standard for the Interpolation and Transfer of a Temperature Scale in the 800–1600°C Range

The results of an investigation of a standard in the 800–1600°C temperature range are presented. The stability and reproducibility of the standard are determined, and a thermocouple is calibrated at fixed points of silver and copper, and also at higher temperatures using the pyrometer method. The investigations show the advantages of using this standard for the interpolation and transfer of a temperature scale compared with tungsten-strip lamps.     

Emissivity of condensed substances from their thermal radiation spectra

A technique for measuring the temperature and spectral emissivity of condensed substances is described. With this technique, measurements can be made in any spectral range, rather than only at short wavelengths, where the Wien approximation for the Planck formula holds. In particular, in the spectral range around the peak-emission wavelength, the highest signal-to-noise ratio can typically be attained, which raises the accuracy in temperature and emissivity determination. The proposed approach to processing the experimental emissivity curves offers the possibility of analyzing the effects of the major factors (signal-to-noise ratio, spectral range of measurements, type of the model function representing the spectral emissivity, and others) on the accuracy in temperature measurements. The potentialities of the technique are demonstrated by measuring the temperatures and emissivities of W, Re, and Ta strip lamps in the spectral range 0.9 to 2.1 Μm.     

Upgradation of a spectral irradiance measurement facility at National Physical Laboratory,India

This report describes the details of a recently upgraded spectral irradiance measurement facility in optical radiation standards at National Physical Laboratory, India. This facility provides the calibration of spectral irradiance in the wavelength range 280 nm – 2500 nm. PTB, Braunschweig, Germany calibrated five numbers of 1000 W quartz halogen lamps, which are used as reference standards for spectral irradiance scale. In addition to providing the details of instruments, the procedure of calibration and evaluation of uncertainties is also described. For checking the fidelity, repeatability and reproducibility of the upgraded system, calibration of one of the PTB calibrated lamps, was done against the other four PTB calibrated lamps. These measurements not only provide confidence on the upgraded system but also verify the retention of the PTB certificate values after a lapse of two years after their calibration.     

红外测温系统在航空发动机轮盘试验中的应用

该文论述了红外测温基本理论和红外测温仪工作原理,设计开发了适用于航空发动机轮盘试验的非接触红外测温系统,分析影响红外测温系统测量准确度的主要因素,研究发射率的确定方法,在轮盘静止和旋转状态下进行了试验验证。其结果表明:影响红外测温系统测量准确度最重要的因素是发射率;用热电偶对发射率进行确定的方法是可行的;轮盘在静止和旋转状态下的发射率相同,静止状态下确定的发射率可用于旋转状态下的温度测量。     

Development of High-Temperature Fixed Points of Unknown Temperature Suitable for Key Comparisons

During the last key comparison of local realizations of the International Temperature Scale of 1990 above the silver point, which used high stability tungsten strip lamps, it became clear that these artifacts can no longer be used to evaluate the real calibration and measuring capabilities (CMCs) of the participant laboratories. The intrinsic uncertainty of the lamps is actually larger than the claimed CMCs of most national laboratories. Ideally a set of driftless robust artifacts, preferably of unknown temperature, should be used for this purpose, as this would allow CMCs to be probed at the highest level. Currently such artifacts do not exist. High-temperature fixed points (HTFPs) have been the subject of intense study for more than 10 years. The research has come to an advanced state so much that the temperatures of some of them are well known to be within 1 K. This has rendered their use as comparison artifacts questionable as any comparison would not be blind. To address this issue, doped HTFPs have been developed which have had their transition temperature altered from that of the eutectic composition. Two Ni–C–Cu cells and two Ni–C–Sn were constructed by Inmetro with different quantities of Cu and Sn, respectively. These were compared to a reference Ni–C cell (nominal transition temperature of 1329  \(^{\circ }\) C) and the temperature differences from the pure state determined. In this paper the design, construction, and results of long-term stability are described. These promising results indicate that it is possible to make HTFPs with altered temperatures which are stable enough to serve as comparison artifacts.     

Temperature Measurement Technique for Stabilizing the Light Output of RGB LED Lamps

The efficiency of light-emitting-diode (LED) lights approaches that of fluorescent lamps. LED light sources find more applications than conventional light bulbs due to their compactness, lower heat dissipation, and real-time color-changing capability. Stabilizing the colors of red–green–blue (RGB) LED lights is a challenging task, which includes color light intensity control using switching-mode power converters, color point maintenance against LED junction temperature change, and limiting LED device temperature to prolong the LED lifetime. In this paper, we present a LED junction temperature measurement technique for a pulsewidth modulation diode forward current controlled RGB LED lighting system. The technique has been automated and can effectively stabilize the color without the need for using expensive feedback systems that involve light sensors. Performance in terms of chromaticity and luminance stability for a temperature-compensated RGB LED system will be presented.      

Metrological features of color pyrometry

Summary An examination of the sources of errors leads to the conclusion that in many instances the methods of color pyrometry can improve the precision of industrial temperature measurements. This is the case in the measuring of the temperature of oxidized and other surfaces with a rough structure, of clean surfaces of many metals in different conditions, of components in closed furnaces (through windows, etc.). and in many other cases. Objective color pyrometers are particularly useful, for they have a high instrument accuracy and measure directly the redblue ratio. However, in making the color measurements it should be remembered that the selective, especially the changing, emission or absorption produces an error which often exceeds the error of the brightness method.     

Profile measurement taken with liquid-crystal gratings

Profile measurement taken with liquid-crystal gratings and a phase-shifting technique is proposed, and its effectiveness is verified by experiment. The surface profile is obtained by measurement of the phase distributions of the sinusoidal gratings deformed by an object's surface. The liquid-crystal grating gives an accurate phase shift, an arbitrary projection pitch, and a constant surface brightness compared with conventional gratings such as a laser interference fringe grating and a Ronchi grating. Therefore a flexible measuring system may be developed with it. Two gratings with different pitches are used to measure an object with large steps. A two-color projection system can be used to produce such gratings simultaneously. Locally varying reflectivity on a surface can also be compensated by adjustment of the color component of the projected grating with a liquid-crystal grating. Thus the contrast in the projected grating can be made uniform, and a good profile measurement can be accomplished.     

A Nickel–Carbon Eutectic Cell for Contact and Non-contact Thermometry

The highest-temperature, defining fixed point of the International Temperature Scale of 1990 (ITS-90) is the copper freezing point (1,084.62°C). Many international metrology institutes are investigating the use of transition temperatures of metal–carbon alloys as references for the calibration of temperature measuring instruments above the copper point, making it possible to reduce the calibration uncertainty of pyrometers in radiation thermometry and thermocouples in contact thermometry. This research is being performed mainly by radiation thermometry laboratories that have developed specific cells with blackbody cavities containing relatively small quantities of metal–carbon alloys. Parallel to this, some laboratories have also developed cells with these same alloys, but of a different design, suitable for the calibration of thermocouples. This report concerns the development of a nickel–carbon eutectic cell (≅1,329°C) at Inmetro, with which either a radiation thermometer or thermocouple can be calibrated. The measurements of the temperature of this cell were performed using the reference radiation thermometer of the Pyrometry Laboratory and Pt/Pd thermocouples that were constructed, stabilized, and calibrated at the Thermometry Laboratory. Details of the cell fabrication, as well as the instrumentation used for the measurements are given. The results of a comparison between the two different types of measurement are reported, including the uncertainty budgets of both methods.     

多波长可视化测温系统标定的实验研究

讨论了一种基于光学的火焰／温度场测量系统的标定方法。借助黑体炉等标定源,利用温控系统提供温度参数,经CCD系统成像得到图像的灰度值,通过函数拟合获得辐射图像灰度与温度之间的关系。通过调整不同的快门速度,扩大了CCD的动态范围,从而扩大测温范围。应用图像处理技术对辐射图像去噪,对标定数据进行了整理和拟合,并对结果进行了分析。     

CCD相机的亮度色度校准装置研制

CCD相机的亮度和色度测试仪器凭借其一系列的测量优势已广泛应用于平板显示器的测量领域。本文在综合国内外相关计量标准技术优势的基础上,根据平板显示行业所特有的溯源需求进行校准装置的研制,基于积分球匀光和光谱测色原理,研制出CCD相机的亮度色度校准装置,并对校准装置的计量性能和特性进行研究以及对装置的测量结果进行验证。结果表明,该校准装置满足作为计量标准的技术要求,可用于CCD相机亮度和色度参数的校准。     

High-speed digital color imaging pyrometry

Temperature measurements of high-explosive and combustion processes are difficult to obtain due to the speed and environment of the events. To overcome these challenges, we have characterized and calibrated a digital high-speed color camera that may be used to measure the temperature of such events. A two-color ratio method is used to calculate a temperature using the color filter array raw image data and a graybody assumption. If the raw image data are not available, temperatures may be calculated from the processed images or movies, depending on proper analysis of the digital color imaging pipeline. We analyze three transformations within the pipeline (demosaicing, white balance, and gamma correction) to determine their effect on the calculated temperature. Using this technique with a Phantom color camera, we have measured the temperature of exploded C-4 charges. The surface temperature of the resulting fireball was found to rapidly increase after detonation, and subsequently decayed to a constant value of approximately 1980 K.     

Illumination source identification using a CMOS optical microsystem

An integrated silicon color sensor system has been designed and fabricated in CMOS without extra masks for color filtering. The application is in low-cost measurement of ambient light conditions, e.g., for display control in portable instruments, or for testing the intensity and spectral distribution of light sources. Signals proportional to the intensity and the spectral distribution of the incident light are available at the output in the form of two bit-streams. It is demonstrated that daylight can be distinguished from other light sources, such as incandescent lamps and fluorescent lamps.     

Microhotplate Temperature Sensor Calibration and BIST

In this paper we describe a novel long-term microhotplate temperature sensor calibration technique suitable for Built-In Self Test (BIST). The microhotplate thermal resistance (thermal efficiency) and the thermal voltage from an integrated platinum-rhodium thermocouple were calibrated against a freshly calibrated four-wire polysilicon microhotplate-heater temperature sensor (heater) that is not stable over long periods of time when exposed to higher temperatures. To stress the microhotplate, its temperature was raised to around 400 °C and held there for days. The heater was then recalibrated as a temperature sensor, and microhotplate temperature measurements were made based on the fresh calibration of the heater, the first calibration of the heater, the microhotplate thermal resistance, and the thermocouple voltage. This procedure was repeated 10 times over a period of 80 days. The results show that the heater calibration drifted substantially during the period of the test while the microhotplate thermal resistance and the thermocouple-voltage remained stable to within about plus or minus 1 °C over the same period. Therefore, the combination of a microhotplate heater-temperature sensor and either the microhotplate thermal resistance or an integrated thin film platinum-rhodium thermocouple can be used to provide a stable, calibrated, microhotplate-temperature sensor, and the combination of the three sensor is suitable for implementing BIST functionality. Alternatively, if a stable microhotplate-heater temperature sensor is available, such as a properly annealed platinum heater-temperature sensor, then the thermal resistance of the microhotplate and the electrical resistance of the platinum heater will be sufficient to implement BIST. It is also shown that aluminum- and polysilicon-based temperature sensors, which are not stable enough for measuring high microhotplate temperatures (>220 °C) without impractically frequent recalibration, can be used to measure the silicon substrate temperature if never exposed to temperatures above about 220 °C.     

Measuring the distance and orientation of a planar surface usingnonstructured lighting-3-D measurement system for indoor mobile robots

This paper describes a novel method for measuring the distances to planar surfaces and their orientations. The measurement system consists of a TV camera and two ordinary lamps. The lamps are switched on alternately, and images under each lighting condition are taken. If the two light sources are arranged at appropriate positions with respect to the camera, the peak positions in the two images directly give the surface orientation and the perpendicular distance to the plane. By measuring the two peak positions, this method promises to speed up the acquisition of geometrical information on an entire scene considerably because the distance and orientation can be obtained without analyzing range maps. Since the equipment setup is very simple, the proposed technique will be useful, for example, for real-world robotic applications such as navigation of indoor mobile robots. The experimental results on the error of measurement show that the method is sufficient for such purposes     

基于结构相似度的彩色图像质量评价算法

目的研究在Matlab中度量彩色图像之间结构相似度的评价算法,用以评估彩色图像的质量。方法以灰度图像的结构相似度评价模型(SSIM)为基础,在Matlab中将以RGB色空间存储的彩色图像转换到亮度信息和色彩信息分别度量的YUV色彩空间中,设计算法度量彩色图像之间的亮度比较值、对比度比较值和结构比较值,综合三部分后可得彩色图像之间的结构相似度。结果实验结果表明,利用彩色结构相似度算法可以计算彩色图像与参考图像之间的相似度数值,用作质量评价,且其评价结果与人类视觉感知评价(即主观评价)结果保持一致。结论该方法可作为一种新型的彩色图像质量评价准则。