Download JEOL 733 Electron Microprobe Manual

analysis. This guarantees that the sample is also in x-ray focus with the wavelength-dispersive
spectrometers.
When the switch is set to ILM OFF (the center position), no power is supplied to either the OM or the
OMT light sources.
NOTE: The OM source is turned off by setting the switch to ILM OFF (the center position) NOT fully
down -- this is the OMT position and turns on the transmitted light source.
When the switch is set to OMT, the transmitted light source is selected, and the image can be viewed using
either the optical microscope or the camera and monitor. Samples must be in the transmitted light sample
holder in order to be imaged using the transmitted light periscope. SEE WARNING section listed above.
The transmitted light periscope must be inserted for the OMT light source to be aligned properly for
transmitted light imaging. The OM reflected light source is off when the switch is set to OMT.
Note regarding use of the secondary electron detector
When the secondary electron detector is turned on via the SEI switch on the SEI unit, the power to either
the OM or OMT sources is disabled to protect the scintillator of the secondary detector. The OM or OMT
light source will remain off during SEI imaging. When the SEI switch is set to the OFF position, the OM
or OMT light source will turn on within 5 seconds.
Note regarding quality of backscattered-electron imaging
If the OM light source is on while obtaining a backscattered-electron image, you may observe interference
lines on the DISPLAY MONITOR. These are due to 60 hz interference from the reflected light source.
The spacing of these lines depends on the scan rate being used. The available contrast from the BEI-H
detector is compromised when the OM source is on. The BEI unit cannot be used at all if the OM source is
on.
It is best to turn off the OM light source if you are trying to obtain a high quality bse image. The light
should be turned off for photography as well. When it is necessary to optically focus the sample again for
microanalysis, the OM source should be turned back on.
6. OM ILLUMINATION knob
The OM ILLUMINATION knob does not actually vary the brightness of the OM source on our system.
We have a fiber optic light supply that is basically either fully on or off (it uses a slide projector light bulb).
The OM ILLUMINATION sets the threshold; below this threshold setting the fiber optic source simply
turns off, and above this threshold setting the light source is on but at the same brightness regardless of the
knob setting.
For this reason, adjusting the OM ILLUMINATION knob on our system is pointless. Please DO NOT turn
the OM ILLUMINATION down as it will give the impression that the bulb is burned out, when in fact the
setting is below the threshold setting.
7. OMT ILLUMINATION knob
As opposed to the OM ILLUMINATION knob, the OMT ILLUMINATION knob DOES vary the
brightness of the OMT source as a function of the knob position.
If you are using the OMT light source (with the appropriate sample mount, and the OMT periscope inserted
properly), then the brightness of the transmitted light source can be varied by changing the position of the
OMT ILLUMINATION knob.
The OMT ILLUMINATION knob should be set to the 12 o'clock position when not in use.
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