Optical System Overview - Agilent Technologies InfinityLab LC Series User Manual

1 Introduction to the Variable Wavelength Detector

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.
Deuterium lamp
Lens
Sample diode
Flow cell
Beam splitter
Reference diode
Figure 3
Agilent InfinityLab LC Series VWD User Manual
Optical Path of the Variable Wavelength Detector
Filter assembly
Entrance slit
Mirror M1
Grating
Mirror M2
13