Integrating-sphere system and method for absolute measurement of transmittance, reflectance, and absorptance of specular samples

Abstract

An integrating-sphere system has been designed and constructed for multiple optical properties measurement in the IR spectral range. In particular, for specular samples, the absolute transmittance and reflectance can be measured directly with high accuracy and the absorptance can be obtained from these by simple calculation. These properties are measured with a Fourier transform spectrophotometer for several samples of both opaque and transmitting materials. The expanded uncertainties of the measurements are shown to be less than 0.003 (absolute) over most of the detector-limited working spectral range of 2 to 18 microm. The sphere is manipulated by means of two rotation stages that enable the ports on the sphere to be rearranged in any orientation relative to the input beam. Although the sphere system is used for infrared spectral measurements, the measurement method, design principles, and features are generally applicable to other wavelengths as well.

Temperature-Resolved Infrared Spectral Emissivity of SiC and Pt–10Rh for Temperatures up to 900°C

“…Although the covered spectral infrared range is much larger, the main emphasis is on the 2-20 µm region. Custom specialized accessories have been developed to enable transmittance and reflectance measurements of a wide variety of sample types and under the variable control of measurement geometry, beam polarization, and sample temperature [3][4][5].…”

Validation of the Infrared Emittance Characterization of Materials Through Intercomparison of Direct and Indirect Methods

“…Custom absolute methods have been developed for use with the sphere and are described in detail elsewhere [1,4]. The measurement system includes a sample heater unit that can control sample temperatures between 15 • C and 200 • C. The heater is designed to allow both transmittance and reflectance measurements.…”

“…national metrological laboratories, including NIST [1], providing vital data for numerous applications in science and technology. Now these measurements are the most common way of obtaining the spectral directional emissivity (SDE) data, required for non-contact temperature measurements and target discrimination.…”

Tandem Filter Development for Thermophotovoltaic Energy Conversion from January 2003 to February 2006

“…This experimental design presumes that other variables such as the operator, chamber, humidity, and so on can be controlled (that is held constant). 1,13,8,7,11,10,16,14,3,9,19,6,4,18,15,20,17 Only the runs for resistive heating of GaTe were completed. The results showed unacceptable absorption occurred for all combinations of the independent variable.…”