Analysis of light-scattering samples
Integrating sphere
94 Edition 09/2014 SPECORD S600 accessories
20.2.2 Reflectance measurements
Store Spectralon inserts carefully!
Store references of Spectralon carefully to avoid any damage to their surface or
contamination.
The colored appearance or the gray tone of an opaque body is due to its
wavelength-dependent diffuse backreflection (diffuse reflectance). Reflectance
measurements can be performed with different illumination and measurement
geometries depending on the surface structure of the sample.
To preclude the effect of the surface structure as far as possible, the sample
surface is diffusely illuminated by means of the integrating sphere. The quartz
lens (7 in Fig. 20-1) images the sample surface onto the entrance slit of the
spectrometer.
The reflectance of the sample is the ratio of the radiation reflected from its
surface and the radiation reflected from a completely matt white surface of a
standard (e.g. a Spectralon standard) under the same optical conditions.
For this purpose, you can use one of the two Spectralon inserts supplied with
the equipment.
The integrating sphere is preferably used for reflectance measurements of
textured (rough, grained, etc.) surfaces, such as cellulose, leather or fabrics and
of samples with azimuthal gloss, i.e. a gloss that varies while rotating the
sample about its surface normal, and for powdery samples.
For solid samples, choose the horizontal position of the sphere body. In this
position, you can replace the samples without the need for removing the sphere
body from the sample compartment.
For powdery samples, choose the vertical position.
Fig. 20-8 shows the integrating sphere in reflectance measurements.
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