Accurately measuring the spectral emissivity is of significant importance in thermal radiation. In this study, an improved measurement method for determination of spectral emissivity via modulating the surrounding radiation is proposed. A proof-of-concept measuring apparatus is constructed, and the main component parts are described in detail. The temperature uniformity of the isothermal aperture is verified, and the impact of the temperature uniformity on the emissivity measurements is studied. The good linearity and long-term stability of the detector is evaluated to ensure the validity of the improved method. The potential reference materials (silicon carbide and Armco iron) were used to validate the reliability and the accuracy of the measurement apparatus. The excellent data consistency of both two reference materials with the literature data demonstrates the reliability of the improved method and the measurement apparatus. The performance of the measurement apparatus with and without the isothermal aperture is compared, and the necessity of the modulated surrounding radiation is validated. The calculated combined uncertainty for the SiC sample at 1073 K is better than 2.38 %. The superior performance of the emissivity measurement apparatus indicate that the improved method proposed in this work provides a new approach for accurately measuring the spectral emissivity.

准确测量光谱发射率在热辐射中具有重要意义。在这项研究中，提出了一种通过调制周围辐射来确定光谱发射率的改进测量方法。构建了一个概念验证测量装置，并详细描述了主要组成部分。验证了等温孔径的温度均匀性，研究了温度均匀性对发射率测量的影响。对检测器良好的线性度和长期稳定性进行了评价，以保证改进方法的有效性。潜在的参考材料（碳化硅和 Armco 铁）用于验证测量设备的可靠性和准确性。两种参考物质与文献数据的良好数据一致性证明了改进方法和测量装置的可靠性。比较了有无等温孔径测量装置的性能，验证了调制周围辐射的必要性。SiC 样品在 1073 K 时的计算组合不确定度优于 2.38 %。发射率测量装置的优越性能表明，本文提出的改进方法为准确测量光谱发射率提供了一种新方法。并验证了调制周围辐射的必要性。SiC 样品在 1073 K 时的计算组合不确定度优于 2.38 %。发射率测量装置的优越性能表明，本文提出的改进方法为准确测量光谱发射率提供了一种新方法。并验证了调制周围辐射的必要性。SiC 样品在 1073 K 时的计算组合不确定度优于 2.38 %。发射率测量装置的优越性能表明，本文提出的改进方法为准确测量光谱发射率提供了一种新方法。