White Reference - ASD TerraSpec User Manual

www.asdi.com
Step 7
Step 8
Step 9
Step 10
Step 11
Step 12
6.4

White Reference

ASD Document 600541 Rev. G
The project screen will return, and the sample count will be displayed in the
status box at the bottom of the graph.
Make sure the light source is on and the probe input end is pointed at the
white reference panel.
Select Spectrum->Take a Baseline [Alt+S, B] [Ctrl+R]. When
prompted, click Yes, take a new white reference.
• The TerraSpec spectrometer optimizes the detector sensitivities for the
probe and light source currently being used.
• The dark offset and white reference will also be measured and saved.
• Status bars will indicate each process.
When optimization and white reference are complete, you should see a
straight baseline across the Project Graph at 1.00 (100%).
Select the Display->Reflectance [Alt+D, R] for the reflectance mode.
Place the sample on the white reference panel and the spacer end in contact
against the sample.
This assumes that your reflectance probe has appropriate spacing or spacers
on the end.
Press the Space Bar once or select the Spectrum->Take a Scan [Alt+S,
T].
When the TerraSpec spectrometer finishes recording and averaging the
Spectra, the graph in the project window will be updated to show the
reflectance spectrum of the sample.
Observe samples.
A material with 95-99% reflectance across the entire spectrum is called a
white reference panel or white reference standard.
The raw measurement made by the spectrometer is influenced by both the
sample and the light source. An independent measure of the light source
illumination on a reference of known reflectance is required to calculate the
reflectance of the sample. The use of a white reference standard with near
100% reflectance simplifies this calculation.
The ASD application software, such as RS
ratios for reflectance or transmittance of the material being sampled by the
TerraSpec spectrometer using the white reference as the standard.
Spectralon from Labsphere is the white reference standard that is very
suitable for the VNIR and SWIR spectral ranges of ASD instruments.
38
Chapter 6 Field Measurements
3
and Indico, can calculate the
TerraSpec® User Manual