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Section IV-C: Focusing and Alignment of Array Detectors
With the array detector properly mounted to the SP-2300i, use the following procedure to align and focus the
array detector to the SP-2300i optical system. It is assumed that the array detection system is running with
SpectraSense or WinSpec.
1. Mount a light source such as a mercury pen-ray type to the entrance slit of the SP-2300i. Princeton
Instruments offers a standard mercury lamp, Model MS-416, designed for this purpose. Any light
source with line output can be used. If there are no “line” sources available, it is possible to use a
broad band source such as tungsten for the alignment. If this is the case, use only a wavelength
setting of 0.0 nm for alignment purposes.
2. With the SP-2300i properly connected to the controller or computer, turn the power ON and move the
spectrograph to a wavelength of 435.8 nm if using a mercury lamp, or 0.0 nm for a broad band source,
or another wavelength corresponding to a spectrum produced by another “line” source.
3. With the array detector operating, check the image of the light source if running in an imaging mode
with a CCD. Otherwise check the line intensity and shape.
4. Using a 1/8” Allen wrench, loosen the two (2) #10-32 set screws (approximately 2 turns) located on the
top and side of the front plate, and slowly slide the array detector IN or OUT until the sharpest image is
achieved, or the sharpest line is achieved.
CAUTION: The set screws must be loose when turning the thumb wheel adjustment,
or severe damage will occur. The distance between the edge of the array
detector mounting flange and the instrument MUST NOT exceed .33”.
5. Move the thumb wheel until it just makes contact with the array detector mounting flange. This enables
you to rotate the detector without changing the focus position. Rotate the detector for correct
alignment. The thumb wheel adjustments may be use d to precisely position the detector -one eighth
of a turn of the thumb wheel changes the detector position by approximately 1/10th of a millimeter.
6. After each adjustment, ensure the array detector mounting flange is in contact with the thumb wheel
and the two (2) push screws. Tighten the #10-32 set screw on the top of the front plate first, and then
tighten the one on the side to secure the detector.
7. Best spectral resolution is obtained when the array detector is aligned to the SP-2300i. The light
source can be removed if desired, and replaced by fiber optics or other light sources.
8. If fibers or other imaging optics are used to bring light into the SP-2300i, they may require adjustment
along the optical axis to achieve best vertical image quality.