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2. SYSTEM DESCRIPTION
Figure 2.5: Top View of Spectrophotometer
FOREOPTICS Refer to Figure 2.4 and Figure 2.5
The automated system drives stepper motors which control three elements in the foreoptics
assembly - the Iris Diaphragm, Filterwheel #1, and Filterwheel #2. The associated driving and
sensing electronics are integrated into the Main Electronics board. The Brewer software
automatically controls motors once the Configuration File has been appropriately configured.
Incoming light is directed through the foreoptics by the director prism [ZP 1], which may be rotated
to select light from either the zenith sky, the direct sun, or one of the two calibration lamps. A
mercury lamp provides a line source for wavelength calibration of the spectrometer, while a quartz-
halogen lamp provides a well regulated light source so that the relative spectral response of the
spectrometer may be monitored. Elements in the foreoptics provide adjustment for field-of-view,
neutral-density attenuation, ground-quartz diffusion, and selection of film polarizers.
Iris Diaphragm Assembly
An iris diaphragm [IR 1] is mounted in the foreoptics at the ultraviolet focus of a plano-convex lens
[LE 2]. This lens focuses ultraviolet objects at infinite distance onto the plane of the iris. A lever arm
which protrudes through the wall of the foreoptic tube controls the iris. At one limit of the lever arm
the iris aperture is 5mm ( iris closed), while at the other limit the aperture is approximately 15mm
(iris open). The lever is actuated by the iris stepper motor.
15
MKIII OPERATOR'S MANUAL
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