Ocean Optics OOIColor - Manual (Page 9)

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Experiment Tutorial
Reflective Color – An Overview
Ocean Optics offers several experimental arrangements to measure reflective color: our R200
fiber optic reflection probe, our ISP-REF integrating sphere or a custom geometry using optical
fibers and collimating lenses (74-VIS or 74-UV). All measurements produce valid results. The
choice of method is based on your experimental requirements and any procedural restraints such
as industry standards.
The R200 reflection probe consists of a bifurcated optical fiber bundle consisting of seven 200
µ m optical fibers arranged in a six-around-one configuration. The outer six optical fibers provide
even surface illumination to your sample, while the central fiber reads the reflection from your
sample. The optical fiber probe is Y-shaped, with two arms of the Y being terminated in SMA
connectors, and the third leg terminated in a ¼” stainless steel tube. The end with the stainless
steel tube is the probe end of the fiber, and is positioned near your surface (our reflection probe
holder RPH-1 is ideal for this purpose). The other two ends of the optical fiber probe go into the
light source and the spectrometer; their orientation is extremely important. Look carefully at the
ends of the SMA connectors, and you will see that one has a hole that is about three times larger
than the other. The fiber leg with the larger hole MUST be placed in the light source. The leg
with the smaller hole is placed in the spectrometer.
Ocean Optics also offers an integrating sphere specifically designed for color measurements. The
inside of the sphere is illuminated with a tungsten-halogen light source, which will provide the
surface to be analyzed with even, non-directional surface illumination. An optical fiber is then
placed in the SMA port marked S, and the other end of the fiber is installed in your spectrometer.
The reference or sample is placed over the 1-cm orifice. There is a switch on the integrating
sphere marked E and I. This switch opens and closes a small port on the inside of the integrating
sphere, which
I ncludes or E xcludes the contribution of specular reflection from the sample.
Reflective Color Measurements with a White Standard
The first step in making a reflective color measurement is to take a spectrum of a physical
standard. This standard can be a 100% reflective white standard, such as Ocean Optics part WS-1.
The spectrometer response will be set to 100% reflective at all wavelengths.
Before making this measurement in OOIColor, it is a good idea to make the measurement in
OOIBase. The OOIBase program will allow you to see the scope-mode spectrum acquired in real-
time, and to ensure that the spectrometer is receiving the proper amount of light. If you notice that
the spectrometer is saturated, you must either reduce the integration time of the spectrometer (see
Parameters worksheet page above), or reduce the amount of light entering the optical fiber. If you
are using an R200 fiber optic probe, you can easily reduce the amount of light entering the
spectrometer by simply moving the fiber probe farther away from your surface. If you are using
the integrating sphere, the only way to reduce the amount of light entering the optical fiber is to
use a fiber of smaller core diameter.