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NOTE
For high accuracy alignment and installations where there is
less than 0.5 metres (20 inches) between the laser and mirror,
perform steps 5 through 7.
Remove the receiver alignment target and plane mirror interferometer alignment
target and rotate the turret of the laser head to select the large aperture. Do not re-
move the plane mirror interferometer alignment aid on the output side of the plane
mirror interferometer.
With a fast responding voltmeter (preferably a meter type) attached to the receiver
test point, fine adjust the plane mirror interferometer angularly until a signal is re-
ceived on the receiver. (The voltmeter will suddenly jump to some value greater than
0.25 volts.) This is a critical adjustment and may initially require great care to achieve
the desired result.
Peak the voltmeter reading (which will be fluctuating) by fine adjusting the plane
mirror interferometer in both angular axes. This aligns the laser beam to within k15
arcseconds to the mirror. If the mirror has been aligned to the direction of travel
within +I5 arcseconds, the laser beam will be aligned to the direction of travel within
+30 arcseconds, or approximately 0.04 parts per million. That is, 0.04 micrometre of
travel (0.04 microinches per inch) of cosine error.
Lock down the plane mirror interferometer securely, making sure the alignment is
not disturbed.
Remove the plane mirror interferometer alignment target and alignment aid. The
reference beam and the measurement beam must be centered on the receiver align-
ment target.
10.
Remove the receiver alignment aids and rotate the turret on the laser head to the
large aperture. Verify that the LED indicator on the receiver is illuminated and the
voltage at the receiver test point is between 0.6 and 1.5 Vdc.
NOTE
Steps 11 through 20 constitute the X-axis alignment.
With the laser head turret in the large aperture position, place the plane mirror inter-
ferometer alignment target on the laser head side of the X-axis plane mirror interfero-
meter and the receiver alignment target on the receiver (Figure
2-53c,
position 1).
Place a piece of opaque material between the X-axis plane mirror interferometer and
the mirror.
Angularly adjust the 50% beam splitter until the laser beam enters one hole of the
plane mirror interferometer alignment target and exits the other centered on the
receiver alignment target (do not adjust the laser head). Slight lateral adjustments of
the 50% beam splitter may be necessary to ensure there is no beam clipping. Lock
down the 50% beam splitter securely.
Select the small aperture on the front turret of the laser head and install the alignment
aid on the output of the plane mirror interferometer in the correct orientation. Remove
the opaque material from between the plane mirror interferometer and the mirror.
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Table of Contents
Troubleshooting
