270M
Rapid
Scanning Imaging Spectrograph
1 Overview
of
the 270M:
The
270M
is a
new
generation spectrometer.
It
includes several
new
innovations,
along
with
the best
of
proven technology and features.
1.1
Total Automation:
All moving parts
of
the
270M
are automated. The slits, scanning drive, and
optional turret, shutters, and side port selection mirrors are controlled remotely
by
any
of
several computer/ software options
or
the HandScan via the optional
SPEX232 interface. You can alter system performance and function
as
necessary
without
direct access
to
the instrument.
With
computer program control,
it
is
possible
to
automatically adjust bandpass, change gratings,
switch
detectors or
inputs
without
operator intervention.
1.2 Rapid Scanning Wavelength
Drive:
A unique high speed sine drive moves the
270M'
s grating in steps
that
correspond
to
linear increments
of
wavelength change
at
the exit slit, or the center pixel
of
an
array detector. The constant step size simplifies control, and eliminates the
possibility
of
disparities in scanned data
that
could arise from using a direct
worm
drive
that
may have significant unevenness
of
wavelength movements. For
1200
g/mm gratings a step equals
0.03125
nm. Step sizes
for
all other grating
groove densities can be calculated by applying
an
inversely proportional scale
factor. For example: a
300
g/mm grating would move
O.
125
nm per step. This
conversion is done automatically by Spex controllers and
software.
1.3 Optical Design Optimized for Imaging:
Optical performance is radically improved over earlier designs
by
a unique Czerny-
Turner configuration utilizing a proprietary aspheric optical correction. The optical
. correction provides
for
exceptional imaging capabilities. Astigmatism, fnherent in
classical Czerny-Turner systems, is negligible. The fast (f/4) system delivers near
perfect spectral imaging over an area
25
mm wide
by
12
mm
high in the
spectrograph image plane. The computer aided geometric design prevents
rediffracted light
from
reaching the detector.
With
other designs this rediffracted
light can
be
detected as a spurious signal.
Revilled
November
24,
1992
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