MCS260
CORNERSTONE 260 MONOCHROMATORS
39
11 GRATING INSTALLATION AND CALIBRATION
Grating installation and field calibration are typically performed at one of Newport’s manufacturing
location, or by qualified field service personnel. The instructions provided in this section are for advanced
users only.
11.1 RECALIBRATION SERVICES
Newport suggests that monochromators be returned annually for service. In addition to verifying
the calibration, the instrument would be fully inspected. Any refurbishment required, such as fresh
lubrication on the worm gear, would be included in the servicing of the instrument.
11.2 SETTING THE WAVELENGTH OFFSET
A wavelength offset is used to shift the wavelength position to either a higher or a lower
wavelength. For example, if a HeNe laser operating at 632.8 nm is sent through the
monochromator and the output is visible when the monochromator is set to 640 nm, an offset can
be introduced.
When performing this procedure, it is necessary to use a light source with a known spectral line
appearing within the operating range of the grating. Oriel offers a number of pencil calibration
lamps for this purpose, such as the model 6035 Hg lamp. Another line source such as a laser may
also be used. Always be sure to follow the appropriate safety precautions when dealing with any
light source.
Procedure:
1. Select a radiation source that has at least one narrow spectral line in the
wavelength region of interest.
2. Select a detector with an operating range appropriate for the spectral line.
3. Focus the radiation onto the entrance slit (the monochromator is F/3.9). Note that
a narrower slit provides greater resolution.
4. Ensure the focused beam is parallel to the monochromator’s optical axis.
5. Command the monochromator to select the grating for which the offset is to be
applied to.
6. Use the STEP command to move the grating position until the spectral line is
visible at the output.
7. Use the CALIBRATE command to enter the exact wavelength of the spectral line.
The Cornerstone wavelength offset has now been entered into memory. This
offset applies to all other wavelength positions when using this grating.
8. Repeat the process for the second and third gratings, if required. Depending on
the configuration, the monochromator may have two or three gratings installed.
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