An optical fiber bundle displacement sensor with subnanometer order resolution
and low thermal drift is proposed. The setup is based on a carrier amplifier
system and involves techniques to eliminate fluctuation in the light power of
the source. The achieved noise level of the sensor was . The stability was estimated by comparing the outputs of two
different sensors from the same target for 4 ks (67 min). The relative
displacements between the fiber bundle ends of the two sensors and the target
surface varied in the area of 400 nm depending on the ambient temperature
variation at 2 °C. However, the difference in output between the two sensor
systems is within 2 nm for more than 1 hour of measurement. It is expected that
it would be reduced to within the area of 0.1 nm if the ambient temperature were
controlled to within ±0.1 °C. It is concluded that the stability of the sensors
is sufficiently good to be used with nanotechnological instruments.
© 1995 Optical Society of America
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