ACTIVE SUPPRESSION OF ACOUSTICALLY-INDUCED
OPTICAL JITTER
Jitter
is the deviation of the Line-of Sight (LOS) between an optical
train and a point in space. Caused by optical component vibration,
jitter is detrimental to applications involving accurate position
and pointing control. These applications include laser
communication, astronomical telescopes, optical switches,
earth-observing satellites, and semiconductor manufacturing.
Feedback and feedforward control is being investigated to mitigate
jitter in such an optical system. A position-sensing detector,
accelerometers, and microphones are used to sense the disturbance
and a fast-steering mirror (FSM) is actuated accordingly to
compensate for the optic motion.
Figure
1. The experimental testbed inside the anechoic chamber at Duke
University.
The laser source and position sensing detector are mounted
inside an acoustic isolation enclosure on one optical bench, while
the turning mirror and FSM are mounted on a second bench and
exposed to an acoustic disturbance.
Figure
2. Y-axis jitter spectrum before and after control is applied;
50-state controller using a microphone as a feedforward sensor,
FSM as an actuator.
This
work is generously supported by NSF/CMS Ind./ University Research
(Sup. GOALI) Grant # CMS-9908271.
Research
performed by Mark A. McEver and Robert
L. Clark.
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