Varian ProStar 325 UV-Vis, Service Manual

Page: 96 / 149

ProStar325 Service Manual
96
Publication date 8 May 2003
5 Optics
5.1 Introduction
The photometric performance of any detector is largely
determined by the quality of the monochromator. With UV-Vis
detectors, the monochromator design is aimed at providing a
desired wavelength resolution while maintaining high light
throughput and low stray light.
The optics must;
•
Efficiently couple light from the lamps to the mono
•
Split the light into sample and reference beams without
excessive light loss
•
Focus these beams into the flowcell compartment
•
Collect the light from the monochromator and direct it to
the photodiode detectors.
The ProStar 325 optics is designed around a Cerzy-Turner style
monochromator. This is a single-pass monochromator, using
quartz over-coated optical components. The detector is capable of
operating in the range from 175-900nm. Dual silicon photodiode
detectors provide an output for measurement by the electronics
system.
It is not possible to perform any optical alignment or replace any
optical components within the ProStar 325. The optics module is
designed to be replaced as a complete assembly.
5.2 Optics module
The optics module contains the UV and Vis source lamps, source
optics, beam splitter, entrance & exit masks, monochromator and
mirror assemblies that form the sample and reference beams.
This module is located towards the front of the detector and can
be easily removed and replaced if necessary as described later in
this section.
5.2.1 UV lamp assembly
The lamp assembly consists of the Deuterium lamp which is
rigidly cemented onto its mounting bracket. This lamp assembly
is pre-aligned in the factory. There are two securing thumbscrews
on the bracket which also locate the assembly in its proper
position. This ensures that the lamp is properly aligned when it
is mounted to the optics module.
When lamp replacement is necessary, it is easily performed by
the user as all lamps come pre-aligned, and no alignment
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