3 PICO
SCALE
FUNDAMENTALS
The
PICO
SCALE
is a powerful system for optical and non-invasive displacement and vibration
measurements. The three channel system is based on a miniaturized Michelson interferometer.
The system features powerful interfaces and
fl
exible software modules. Due to useful accessories
the system can be adapted to speci
fi
c needs. The
PICO
SCALE
GUI allows to operate the system
out of the box. In summary
, these versatile characteristics make the
PICO
SCALE
a very powerful
tool for every lab!
3.1 General setup and basic components
Each
PICO
SCALE
measurement setup requires a few basic components. The
PICO
SCALE
con-
troller is the core component.
I
n the controller, coherent light is generated by a laser diode. A
fi
ber network distributes the laser light into three output channels.
Sensor head
Reference
mirror
Target mirror
Working distance
Optical fiber
PICO
SCALE
Figure 3.1: Basic setup of a
PICO
SCALE
displacement measurement. Miniaturized sensor heads
are connected to the
PICO
SCALE
controller via optical
fi
bers. The system measures
the displacements of a target mirror relative to the sensor head.
Up to three sensor heads can be connected to the controller via optical FC/APC-terminated
fi
bers.
Within the sensor head, the laser light is divided into a reference and a measurement beam by
a beam splitter, being the central component of a Michelson interferometer.
I
n standard sensor
heads one side of the miniaturized beam splitter cube is coated with a re
fl
ective coating, which acts
as reference mirror. The measurement beam exits the head and is re
fl
ected by the measurement
target, which can be a mirror, a piece of glass or almost any other technological relevant surface.
Both, the re
fl
ected reference and measurement beam interfere in the center of the beam splitter
cube and the combined light is guided back to the controller. Due to advanced signal processing
methods, based on lock-in detection and fast FPGA based evaluation algorithms, the
PICO
SCALE
is able to measure target mirror displacements with single picometer resolution and sample rates
of up to 10 MHz.
16
PicoScale User Manual
