Optical System Overview - Agilent Technologies G1314B VWD User Manual

Optical System Overview

The optical system of the detector is shown in
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 (in position none, cut-off or holmium oxide), 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.
Deuterium lamp
Lens
Sample diode
Flow cell
Beam splitter
Reference diode
Figure 1 Optical Path of the Variable Wavelength Detector
1200 Series Variable Wavelength Detector User Manual
Introduction to the Variable Wavelength Detector
Figure 1. Its radiation source is
Filter assembly
Entrance slit
Mirror M1
Grating
Mirror M2
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