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Agilent 1260 Infinity VWD User Manual 11
Introduction to the Variable Wavelength Detector
1
Optical System Overview
Optical System Overview
The optical system of the detector is shown in the figure below. Its
radiation source is a deuterium- arc discharge lamp for the ultraviolet (UV)
wavelength range from 190 to 600 nm. The light beam from the deuterium
lamp passes through a lens, a filter assembly, an entrance slit, a spherical
mirror (M1), a grating, a second spherical mirror (M2), a beam splitter,
and finally through a flow cell to the sample diode. The beam through the
flow cell is absorbed depending on the solutions in the cell, in which UV
absorption takes place, and the intensity is converted to an electrical
signal by means of the sample photodiode. Part of the light is directed to
the reference photodiode by the beam splitter to obtain a reference signal
for compensation of intensity fluctuation of the light source. A slit in front
of the reference photodiode cuts out light of the sample bandwidth.
Wavelength selection is made by rotating the grating, which is driven
directly by a stepper motor. This configuration allows fast change of the
wavelength. The cutoff filter is moved into the lightpath above 370 nm to
reduce higher order light.
Figure 1 Optical Path of the Variable Wavelength Detector
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