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Chapter 5 Operation 55
4. Slowly move the detector in and out of focus. You should see the spectral line go
from broad to narrow and back to broad. Leave the detector set for the narrowest
achievable line. You may want to use the Focus Helper function (Process|Focus
Helper…) to determine the narrowest line width: it can automatically locate peaks
and generate a report on peak characteristics during live data acquisition (see the
WinSpec/32 on-line help for more information).
Note that the way focusing is accomplished depends on the spectrograph, as follows:
• Long focal-length spectrographs such as the Acton 2300i: The
mounting adapter includes a tube that slides inside another tube to move the
detector in or out as required to achieve optimum focus.
• Short focal-length spectrographs: There is generally
a focusing
mechanism on the spectrograph itself which, when adjusted, will move the
optics as required to achieve proper focus.
• No focusing adjustment: If there is no focusing adjustm
ent, either
provided by the spectrograph or by the mounting hardware, then the only
recourse will be to adjust the spectrograph’s focusing mirror.
5. Next adjust the rotation. You can do this by
rotating the detector while watching a
live display of the line. The line will go from broad to narrow and back to broad.
Leave the detector rotation set for the narrowest achievable line.
Alternatively, take an image, display the horizontal and vertical cursor bars, and
com
pare the vertical bar to the line shape on the screen. Rotate the detector until the
line shape on the screen is parallel with the vertical bar.
Note: When aligning other accessories, such as fibers, lenses, optical fiber adapters,
first align the spectrograph to the slit. Then align the accessory without disturbing the
detector position. The procedure is identical to that used to focus the spectrograph
(i.e., do the focus and alignment operations while watching a live image).
Acquiring Data
Once optimum focus and aperture have been achieved, you can switch from Focus (or
Video Focus) mode to standard data-acquisition operation as determined via the
Experiment Setup dialog box. (In WinSpec/32, you might want to begin with Free Run
(Safe Mode) operation while gaining basic system familiarity.)
This completes First Light for spectroscopy
applications. If the MicroMAX system
functioned as described, you can be reasonably sure it has arrived in good working order.
In addition, you should have a basic understanding of how the system hardware is used.
Other topics, which could be quite important in certain situations, are discussed in the
following chapters. See the appropriate application software manual for information on
using the software to control the system.
Exposure and Signal
Introduction
The following topics address factors that can affect the signal acquired on the CCD array.
These factors include array architecture, exposure time, CCD temperature, dark charge,
and saturation.