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Motion Control Products
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the position of each prism
without interfering with the
clear aperture. These sensors
use a magnet and Hall sensor
positions for each prism are
achieved via on-board motor
drive and control electronics
with a dedicated microproces-
sor and embedded firmware.
Each piezoelectric motor
requires only 3. 3 volts to operate using a full-bridge switch at
the motor resonant frequency
of 110 kHz. No power is needed to hold position.
As the surgeon moves a
pointer on the image from
the video microscope, the
piezoelectric motion system
responds to the pointer input,
rotating the optics to steer the beam to the desired position. First, the path drawn by the surgeon will be transformed into motion profiles
for the beam (both time and position). These
beam motion profiles will be transformed into
separate motion profiles for each prism, which
are then used by the closed-loop motion system to produce the required rotations.
A critical challenge for commercializing the
laser scalpel will be to execute these transformations in near real time, so that surgeons can
actively monitor and make adjustments during
treatment. The piezoelectric motion system has
demonstrated the required mechanical response,
producing continuous rotation of the prisms
with angular velocity of 900 degrees per second
and acceleration of 225,000 degrees per second.
The Memorial Sloan-Kettering team has
For more information
formed a startup company, ColdSteel Laser
( www.coldsteellaser.com), to commercialize the
endoscopic laser scalpel for remote image-guid-
ed endoscopic surgery. With the prototype, the
team has met its initial goals for size, mechanical
speed, accuracy, resolution, competitive costs
and manufacturability. Ongoing development
will focus on real-time control, optimizing the
user interface to meet surgeon’s requirements,
and obtaining FDA certification.
• “The Endoscopic Laser Scalpel: Out of
Figure 2: A Risley prism pair—Rotating two wedge prisms independently around a common rotation
the Lab and into the World,” Memorial
Sloan-Kettering Center News Magazine,
Dec. 2011 http://bit.ly/mdt1310a
• “A New Look at Risley Prisms,” Photonics
Spectra, June 2006 http://bit.ly/mdt1310b
• “UTAF micro motor technology,” New
Scale Technologies, http://bit.ly/mdt1310c
axis allows steering of an incident beam over a continuous range of directions.
Figure 3: An integrated piezoelectric motion system from New Scale
Technologies rotates the beam steering prisms in the endoscope head
with high resolution and small size.