|
CHILR setupwith a large area cavity mounted for
measurement analysis. |
A custom gold integrating sphere based
instrument, which we call the Complete Hemispherical infrared Laser-based Reflectometer (CHILR), is used for
the measurement of the normal directional-hemispherical reflectance of
samples and complex structures such as cavities
used in blackbodies and radiometers. Measurements are made at
10.6 µm using CO2 laser input, a
diffuse-gold-coated 200 mm diameter integrating sphere for
collecting the scattered light, and pyroelectric and MCT
detectors. The addition of other infrared laser wavelengths is
currently underway.
The reflectometeris optimized to measure nearly all the light that
is scattered from the sample into the 2π solid angle in
reflectance (or transmittance) mode. The optimization consists
primarily in the use of a small entrance aperture of the sphere
(6 mm diameter; 1.7° full angle wrt the sample) and laser
input with a correspondingly small beam size (4 mm). This is
in contrast to the 12.5° full angle of the infrared integrating
sphere used for spectral diffuse
reflectance, where the large solid angle is needed to collect
sufficient flux. |
The spatial uniformity and angular dependence of the CHILR can also
be measured for samples and cavities that have minimal amounts of
reflected light into large angles. This is accomplished through a
mount that is held separate from the sphere and incorporates
motorized linear and rotation stages. The sample port size can be
varied up to 50 mm in diameter, and can be used to measure
cavities with aperture sizes up to 50 mm in diameter
(25 mm for complete mapping). |
Spatial Variation of Reflectance of Cavity |
