Di. Milburn et Kgt. Hollands, THE DIRECTIONAL RESPONSE ERROR IN INTEGRATING-SPHERE TRANSMITTANCE MEASUREMENTS AT SOLAR WAVELENGTHS, Solar energy, 55(2), 1995, pp. 85-91
To correctly measure the solar transmittance of a material that scatte
rs light, a detector with uniform directional response must be used, a
nd the integrating sphere is often used in combination with an optical
detector for this purpose. However, no real optical detector system h
as a completely uniform directional response, thus a directional respo
nse error will always exist. This note analyzes the directional respon
se error in directional-hemispherical transmittance measurements at so
lar wavelengths and determines this error for transmittance measuremen
ts on materials that scatter light in different ways, made with a stat
e-of-the-art integrating-sphere-spectrophotometer system. It is shown
that for certain types of materials, the directional response error is
the dominant error in the measurement of directional-hemispherical tr
ansmittance.