Development of a Multiband near-to-far Infrared Radiance COmparator (MIRCO)

In recent years, there has been a growing demand to calibrate industrial blackbodies both at short wavelengths for lower temperatures and at long wavelengths for higher temperatures. User requests cover a very wide temperature range, from  −20°C to 1,500°C in the infrared bands used by thermal cameras or as defined by specific applications (especially the 1–3 μm, 3–5 μm, and 8–12 μm bands). Therefore, LNE (Laboratoire National de Métrologie et d’Essais) has developed a radiance comparator with a mirror-based optical system, an associated set of interference filter wheels, a modular holder for several infrared detectors, and a lock-in amplifier. This setup is designed to be very versatile in terms of wavelength and temperature. Targeted performances have a thermal resolution better than 0.05°C, and a known and controlled size-of-source effect (SSE). A silicon detector and a visible-to-near infrared integrating sphere were used to assess the stray light inside the housing, and supplementary baffles and stops were used to reduce it to an acceptable level. The investigation included measurement of the SSE for this comparator layout. Then, the performance in the 3–5 μm and 8–12 μm bands, using, respectively, indium antimonide (InSb) and mercury cadmium telluride (MCT) detectors, was evaluated using a water heat-pipe blackbody. This paper describes the modeling and the technical solutions implemented to optimize the optical system. Preliminary results are presented for the short-term stability, the thermal resolution between  −20°C and 960°C, and also the SSE up to 60 mm in these bands.     

有效亮度温度理论

经典亮度温度和有效波长理论忽略了环境辐射的影响,且实际测温理论偏离了亮度温度的定义.考虑了环境辐射影响,提出新的有效亮度温度概念,使有效亮度温度适用于存在环境辐射的任意温度测量;进一步提出了基于带通辐射温度计测量的积分有效亮度温度和等效波长理论,使辐射温度计的"主观"测量结果与物体的客观辐射特性相联系,避免了实际测量理论偏离被测量定义.     

100～400K真空红外亮温标准黑体辐射源研制

介绍了中国计量科学研究院研制的100~400K真空红外亮温标准黑体辐射源的工作原理、结构、性能测试方法及测试结果。黑体辐射源通过液氮制冷与3温区控制实现了100~400K范围内的温度控制。在真空环境下,测试了其在温度范围100~400K轴向温度均匀性、底部温度稳定性等技术指标,结果表明均匀性优于0.120K,控温稳定性优于0.020K/20min;在室温大气环境下,利用基于控制环境辐射的发射率测量方法测量了黑体空腔发射率,空腔法向发射率为0.9998。采用基于蒙特卡罗黑体发射率仿真计算方法分析轴向温度均匀性对空腔发射率的影响,分析了标准黑体辐射源的不确定度来源,在8~16 μm波长亮度温度的合成标准不确定度优于0.030K。     

星载光谱辐射亮度绝对定标装置

从光谱辐射亮度的定标原理及其溯源出发,提出并讨论了四种光谱范围在５００ｎｍ￣１０００ｎｍ之间的星载光谱辐射亮度定标系统的设计方案,并进行了具体的方案论证。     

Evaluation of Blackbody Cavity Emissivity in the Infrared Using Total Integrated Scatter Measurements

Deviations from ideal blackbody (BB) behavior can be characterized by a BB’s effective emissivity. The cavity emissivity is most often obtained through a model, given a particular set of input parameters associated with the BB cavity geometry and surface optical properties. It can also be measured directly (radiance) or indirectly (reflectance). A study of BB cavity emissivity using the reflectance method is presented. Several types and designs of blackbody cavities, including those from fixed-point and water bath BBs, using our infrared total integrated scatter (ITIS) instrument for emissivity evaluation are examined. The emissivity is characterized as a function of position on the output aperture, as well as a function of output angle. The measurements have revealed emissivity values, both significantly greater than, and in confirmation of, modeling predictions. For instance, the emissivities of three fixed point BB cavity designs were found to vary significantly despite modeling predictions in the design process of similar behavior. Also, other BB cavities that exhibited poor emissivity performance were re-painted and re-machined, in one case more than once, before the predicted performance was achieved.     

Radiance Temperatures and Normal Spectral Emittances (in the Wavelength Range of 1500 to 5000 nm) of Tin, Zinc, Aluminum, and Silver at Their Melting Points by a Pulse-Heating Technique

The radiance temperatures at four wavelengths (in the range of 1500 to 5000 nm) of tin, zinc, aluminum, and silver at their respective melting points were measured by a pulse-heating technique using a high-speed fiber-coupled four-wavelength infrared pyrometer. The method is based on rapid resistive self-heating of a sample from room temperature to its melting point in less than 1 s while measuring the radiance emitted by it in four wavelength bands as a function of time. A plateau in the recorded radiance-versus-time traces indicates melting of the sample. The melting-point radiance temperatures for a given sample are determined by averaging the measured temperatures along the plateau at each wavelength. The melting-point radiance temperatures for each metal are, in turn, determined by averaging results for several samples. The normal spectral emittances at the melting transition of each metal are derived from the measured radiances at each wavelength and the published values of the thermodynamic (true) melting temperatures.     

Radiance Temperature and Normal Spectral Emittance (in the Wavelength Range of 1.5 to 5 μm) of Nickel at its Melting Point by a Pulse-Heating Technique

The radiance temperature of nickel at its melting point was measured at four wavelengths (in the nominal range of 1.5 to 5 μm) by a pulse-heating technique using a high-speed fiber-coupled four-channel infrared pyrometer. The method was based on rapid resistive self-heating of a specimen from room temperature to its melting point in less than 1 s while simultaneously measuring the radiance emitted by it in four spectral bands as a function of time. A plateau in the recorded radiance-versus-time traces indicated melting of the specimen. The melting-point radiance temperature for a given specimen was determined by averaging the temperature measured along the plateau at each wavelength. The results for several specimens were then, in turn, averaged to yield the melting-point radiance temperature of nickel, as follows: 1316 K at 1.77 μm, 1211 K at 2.26 μm, 995 K at 3.48 μm, and 845 K at 4.75 μm. The melting-point normal spectral emittance of nickel at these wavelengths was derived from the measured radiance in each spectral band using the published value of the thermodynamic (true) melting temperature of nickel.     

一种根据被测对象的真实温度检定红外温度计的新方法

提出了一种检定红外温度计的新方法。应用此方法 ,检定温度计是直接对准被测对象而不是黑体。此外 ,它回避了光谱发射率的测量和温度计光谱响应度的数据。     

有效亮度温度测量中发射率影响的修正

经典的短波高温修正模型不适用于中长波红外温度计的发射率修正和不确定度评定。采用有效亮度温度概念,得到了对于温度范围和测温波长具有广泛适用性的发射率影响模型以及具有简明物理含义的微差近似形式,包含了经典亮度温度理论中的发射率影响修正和环境辐射误差修正。定量分析了经典的短波高温修正模型的误差。针对黑体辐射源的不同溯源方法,讨论了辐射温度计校准中的发射率影响修正方法,并给出修正实例。所用方法可用于辐射测温应用、辐射温度计校准和黑体辐射源校准中的发射率和环境影响修正以及辐射源发射率不确定度对校准结果不确定度贡献的计算。     

Radiance temperatures (at 658 and 898 nm) of niobium at its melting point

Radiance temperatures (at 658 and 898 nm) of niobium at its melting point were measured by a pulse-heating technique. A current pulse of subsecond duration was imparted to a niobium strip and the initial part of the melting plateau was measured by high-speed pyrometry. Experiments were performed with two techniques and the results do not indicate any dependence of radiance temperature (at the melting point) on initial surface or system operational conditions. The average radiance temperature at the melting point of niobium is 2420 K at 658 nm and 2288 K at 898 nm, with a standard deviation of 0.4 K at 658 nm and 0.3–0.6 K at 898 nm (depending on the technique used). The total uncertainty in radiance temperature is estimated to be not more than ±6 K. The results are in good agreement with earlier measurements at the National Institute of Standards and Technology (USA) and confirm that both radiance temperature and normal spectral emissivity (of niobium at its melting point) decrease with increasing wavelength in the region 500–900 nm.Paper presented at the Third Workshop on Subsecond Thermophysics, September 17–18, 1992, Graz, Austria.     

Radiance Temperatures (in the Wavelength Range 527 to 1500 nm) of Palladium and Platinum at Their Melting Points by a Pulse-Heating Technique

The radiance temperatures (at seven wavelengths in the range 527 to 1500 nm) of palladium and platinum at their respective melting points were measured by a pulse-heating technique. The method, based on rapid resistive self-heating of a specimen from room temperature to its melting point in less than 1 s, used two high-speed pyrometers to measure specimen radiance temperatures every 0.5 ms during the heating and melting period. Melting was manifested by a plateau in the radiance temperature-versus-time function for each wavelength. The melting-point radiance temperatures for a given specimen were determined by averaging the measured temperatures along the plateau at each wavelength. The melting-point radiance temperatures for each metal as determined by averaging the results for several specimens at each wavelength are as follows. Based on uncertainties arising from pyrometry and specimen conditions, the expanded uncertainty (two-standard deviation level) is about ±7 K for the reported values in the range 527 to 900 nm and about ±8 K for the reported values at 1500 nm.     

A Simple High-Sensitivity Radiometer in the Infrared for Measurements of the Directional Total Emissivity of Opaque Materials at Near-Ambient Temperatures

A novel device for direct determination of the total directional emissivity of solid surfaces at near-ambient temperatures is described. The method of operation is based on comparing the radiation emitted by the surface with that emitted by a reference. The primary sensor is a solid-state, thermopile detector, and the signal recovery is achieved by phase-sensitive detection techniques, using a mechanical chopper. The device is simple and does not use any cooling. Experimental results are presented using a test sample of clear float glass, kept at 323 K (50°C), with black paint on a float glass substrate as the reference. These results, likely the first for the directional total emissivity of float glass at such low temperatures obtained without cooling, compare well with values in the literature.     

Radiance Temperatures (in the Wavelength Range 521 to 1500 nm) of Rhenium and Iridium at Their Melting Points by a Pulse-Heating Technique

The melting-point radiance temperatures (at seven wavelengths in the range 521 to 1500 nm) of rhenium and iridium were measured by a pulse-heating technique. The method is based on rapid resistive self-heating of the specimen from room temperature to its melting point in less than 1 s and on simultaneously measuring the specimen radiance temperature every 0.5 ms with two high-speed pyrometers. Melting was manifested by a plateau in the radiance temperature-versus-time function for each wavelength. The melting-point radiance temperatures for a given specimen were determined by averaging the measured temperatures along the plateau at each wavelength. The melting-point radiance temperatures for each metal were determined by averaging results for several specimens at each wavelength. The results are as follows. Based on estimates of the random and systematic errors arising from pyrometry and specimen conditions, the expanded uncertainty (two standard-deviation level) in the reported values is ±8K.     

A Database of Normal Spectral Emissivities of Metals at High Temperatures

The normal spectral emissivity and its time variation were measured systematically for a total of thirty kinds of pure metals and alloys at temperatures between 780 and 1200°C. The spectral data were obtained at about 100 wavelengths from 0.55 to 5.3 m under different environmental conditions including oxidation. The spectral data were stored in a database with supplementary information on the specimens. Clear oscillations of the spectral emissivity with time and wavelength were observed for nickel, Inconel, and SUS444 as surface oxidation progressed, while emissivity variations were rather monotonic for other metals such as titanium, cold-rolled steel, and SUS310S. The surface roughness was measured for all specimens by a contact-type instrument before the measurements, and recorded as supplementary information in the database. The database was built on a personal computer operating system (Windows95) to facilitate the dissemination to researchers and engineers interested in the emissivity of metals. Indexes to the emissivity data are metal name, wavelength, temperature, time, and degree of oxidation represented by an effective thickness of oxide film on the specimen surface.     

200 ℃以下红外温度计校准的相关研究

研制了一种可用于200 ℃以下的红外温度计校准的标准黑体辐射源。应用3种不同方法的计算,得到的黑体空腔的有效发射率均在0.997以上。通过一系列的试验,得出工作距离与环境温度是2个重要影响因素,给出了校准中的最佳工作距离,并指出保持温度计环境温度恒定的重要性。     

一种红外温度计的分度新技术

提出了一种与真温有关的分度红外温度计的新方法。该方法把温度计对准材料样品而不是黑体进行分度，其特点是避免了光谱发射率的修正和不要求温度计探测器的光谱响应度的数据，因而具有很大的实用价值。此方法对于工业测温中的重复测量特别有效。     

光谱辐射亮度国际比对与结果分析

基于高温黑体辐射源BB3500M,中国计量科学研究院(NIM)自主研制了第四代光谱辐射亮度国家基准装置,波长范围覆盖220~2550nm,以稳定的钨带灯作为传递标准,改善了测量不确定度。黑体辐射源的温度测量溯源至Pt-C和Re-C固定点黑体,在3021 K采用WC-C固定点黑体进行验证,NIM和全俄光学物理计量院(VNIIOFI)之间的测量偏差小于70 mK。采用新基准装置,NIM参加了光谱辐射亮度国际APMP-PR.S6比对。NIM研制了两套入射光学系统,成像倍率分别为0.58和1.00,立体角为0.006sr和0.008sr,采用两套系统复现光谱辐射亮度量值的差异小于±0.40%。APMP-PR.S6比对结果表明:在紫外、可见和近红外波长范围,NIM与参考值的平均相对偏差分别为0.59%、0.44%和0.34%。全部波长范围的平均相对偏差0.46%。在250nm、400nm、800nm、2500nm波长,光谱辐射亮度的测量标准不确定度分别为0.95%、0.50%、0.41%和0.80%。从而验证了第四代光谱辐射亮度国家基准装置的准确性和可靠性。     

Radiance temperatures at 1500 nm of niobium and molybdenum at their melting points by a pulse-heating technique

Radiance temperatures at 1500 nm of niobium and molybdenum at their melting points were measured by a pulse-heating technique. The method is based on rapid resistive self-heating of the strip-shaped specimen from room temperature to its melting point in less than I s and measuring the specimen radiance temperature every 0.5 ms with a high-speed infrared pyrometer. Melting of the specimen was manifested by a plateau in the radiance temperature-versus-time function. The melting-point radiance temperature for a given specimen was determined by averaging the measured values along the plateau. A total of 12 to 13 experiments was performed for each metal under investigation. The melting point radiance temperatures for each metal were determined by averaging the results of the individual specimens. The results for radiance temperatures at 1500 nm are as follows: 1983 K for niobium and 2050 K for molybdenum. Based on the estimates of the uncertainties arising from the use of pyrometry and specimen conditions, the combined uncertainty (two standard-deviation level) in the reported values is ± 8 K.Paper presented at the Fourth International Workshop on Subsecond Thermophysics, June 27–29, 1995, Köln, Germany.     

(50～500)cd/m2亮度水平下的光谱辐射亮度标准

介绍了一种使用溴钨标准灯、烟熏MgO漫反射白板、国家光强度副基准及国家色温度副基准建立 (5 0～ 5 0 0 )cd m2 亮度水平下光谱辐射亮度标准 (380～ 780 )nm的方法。解决了彩色监视器、彩色显像管、彩色液晶屏的光谱、色度及亮度测量的计量标准问题。     

第四代光谱辐射度和色温度国家基准装置的研制

基于高温黑体辐射源BB3500M研究并建立了第四代光谱辐射度和色温度国家基准装置。采用稳流和稳温相结合的反馈工作模式,开启后3 h即达到温度稳定。3 016 K时,1 h内的温度变化小于0.59 K。温度测量直接溯源至Pt-C和Re-C高温共晶点黑体,2 980 K时的测量不确定度为0.64 K(k=1)。光谱辐射亮度和光谱辐射照度的波长范围向短波分别扩展至220 nm、230 nm,长波扩展至2 550 nm,达到全波段光谱辐射亮度CCPR-S1比对的能力。新基准增加了分布温度参数的测量能力,2 353 K和2 856 K的测量不确定度(k=1)分别改善为1.6 K和2.1 K。对基准装置入射光学系统的辐照不均匀性以及短波紫外大气传输过程所带来的散射和吸收进行了数值计算,提出理论修正方法,将辐照不均匀性测量误差减小0.3%,大气传输误差减小0.29%。