Rgb Lasersysteme QWAVE UV Lux-Meter, illumination measuring device, Brightness meter, DSA491006 Datenbogen
Produktcode
DSA491006
Qwave User Manual
12
Show Loupe
This opens a window with a magnified display of the spectrum around the mouse
pointer. It may be used in order to study small features in the spectrum as an alternative
to zooming in.
pointer. It may be used in order to study small features in the spectrum as an alternative
to zooming in.
3.8 Absorption, Reflection and Transmission Measurements
Principle
In absorption, reflection and transmission spectroscopy you direct light from a
broadband light source onto a sample. Then you take a spectrum !(λ) of the light that is
transmitted through or reflected from the sample. In order to get meaningful results that
are independent of the light source, you also take a spectrum of the light source !
broadband light source onto a sample. Then you take a spectrum !(λ) of the light that is
transmitted through or reflected from the sample. In order to get meaningful results that
are independent of the light source, you also take a spectrum of the light source !
!
(λ) as
a reference.
The spectral transmittance ! λ or reflectance is then simply the fraction of transmitted
or reflected light:
or reflected light:
!(λ) =
!(λ)
!
!
(λ)
This formula gives values in the range between 0 and 1. The transmittance is usually
written as a percentage. The spectral absorbance ! λ is defined as:
written as a percentage. The spectral absorbance ! λ is defined as:
! λ = log
!
!
(λ)
!(λ)
Please note that the absorbance is sometimes defined as the base 10 logarithm and
sometimes as the natural (base e) logarithm. In Waves, you can choose in the Options
window from the File menu which logarithm to use.
sometimes as the natural (base e) logarithm. In Waves, you can choose in the Options
window from the File menu which logarithm to use.
Measurement
In order to measure absorption, reflection or transmission you need to take a reference
spectrum of the light source first. If your measurement setup is not in complete darkness,
it is also generally recommended to take a background spectrum before the
measurement.
spectrum of the light source first. If your measurement setup is not in complete darkness,
it is also generally recommended to take a background spectrum before the
measurement.
To take a background spectrum, turn off the light source, set an appropriate exposure
time and click the “Take Background Spectrum” button [ ] on the Exposure Toolbar. In
order to minimize noise, you may also want to use temporal averaging. When you’ve
taken a background spectrum, you can select the “Use Background Spectrum” button [ ].
If you take a spectrum afterwards, the background spectrum is automatically subtracted
from the measured spectrum, eliminating unwanted background signals.
time and click the “Take Background Spectrum” button [ ] on the Exposure Toolbar. In
order to minimize noise, you may also want to use temporal averaging. When you’ve
taken a background spectrum, you can select the “Use Background Spectrum” button [ ].
If you take a spectrum afterwards, the background spectrum is automatically subtracted
from the measured spectrum, eliminating unwanted background signals.