270M
Rapid Scanning Imaging Spectrograph
270M). Adjust the light intensity until you have a low
to
mid scale signal on the display.
Ideally, set the 270M
to
a wavelength region where several lines are imaged on
various parts
of
the array simultaneously. With multiple lines,
you
can optimize focus
over the entire array. If this is
not
possible, then move the spectrometer drive
to
position spectral lines alternately at the center and ends
of
the array. While observing
the realtime spectral display, rotate the detector
to
minimize the width
of
the image on
the array. Then translate the detector in and out
to
find the best focus.
As you approach the proper focus, the peak will become narrower, and the intensity
will be more concentrated in the central pixels
of
the peak
..
Best focus is reached at
maximum detected intensity in the central pixel. Be careful not
to
be fooled by
apparent intensity fluctuations that may occur as a function
of
small movements
of
a
narrow image being shared between adjacent pixels. For an unintensified array
detector, the full width at half maximum (FWHM) should be 3-4 pixels. For intensified
detectors, ther is a spreading
of
the image due
to
the intensifier, so FWHM will be 4-5
pixels. Be sure that the display
of
your detection system is set
up
to
display intensity
versus pixels. Expand sufficiently on the horizontal pixel axis that you can easily
discern individual pixels.
Optimization
of
the focus adjustment is an iterative process. Repeat the rotation and
translation with successively smaller movements until
no
further improvement is
observed.
If you are using a CCD, it is best
to
check the rotation
of
the detector via an image
display, after obtaining what you think is the best focus and rotation as described
above. If the rotation is correct, the image
of
a spectral line with full slit height should
be perpendicular
to
the x axis.
Through your careful attention during alignment, you
_can
be assured that you will
realize the exceptional performance capability that was designed and built into your
270M
by
Spex.
32-
Revised November
24,
1992
Leica Microsystems, Inc.'s Ex. 1033
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