CHARACTERIZATION OF SPECTRAL EMISSIVITY VIA THERMAL CONDUCTIVE HEATING AND IN-SITU RADIANCE MEASUREMENT USING A LOW-e MIRROR

摘要

A high SNR in-situ measurement of sample radiance in a low-temperature ambient environment is used to accurately characterize sample emissivity for transmissive, low-emissivity samples. A low-e mirror is positioned behind the sample such that the sample and low-e mirror overfill the field-of-view (FOV) of the radiometer. The sample is heated via thermal conduction in an open environment. Thermal conduction heats the sample without raising the background radiance appreciably. The low-e mirror presents both a low emission background against which to measure the sample radiance and reflects radiance from the back of the sample approximately doubling the measured signal. The low-e mirror exhibits a reflectance of at least 90% and preferably greater than 98% and an emissivity of at most 7.5% and preferably less than 2% over the spectral and temperature ranges at which the sample emissivity is characterized.

主权项

1. A method of characterizing the emissivity of a sample, comprising:
a) placing a low-e mirror behind the sample, said sample and said low-e mirror positioned to overfill a field of view (FOV) of a radiometer; b) controlling a heat source to heat the sample through thermal conduction; c) measuring a sample radiance in the FOV over a spectral band with the sample in-situ; d) measuring the temperature of the sample; e) computing an ideal radiance over the spectral band at the measured temperature; f) extracting a calculated sample radiance over the spectral band from the measured sampled radiance; g) computing the sample emissivity as the ratio of the calculated sample radiance to the ideal radiance over the spectral band; and h) repeating steps b through g at increments over a temperature range, wherein said low-e mirror exhibits a reflectance of at least 90% and an emissivity of at most 7.5% over the spectral band for sample temperatures over the temperature range.