MADRID Measurement Apparatus to Distinguish Rotational and Irrotational Displacement

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MADRIDMeasurement Apparatus to Distinguish
Rotational and Irrotational Displacement

• Rafael Ortiz
• Graduate student
• Universidad de Valladolid (Spain)

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MADRID

• Problem to solve
• Reasons of choosing this option
• Description of the device
• First result
• Future works

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Introduction

• High accuracy in microsurgery
• Vitreoretinal microsurgery ?MICRON
• Neurosurgery ?LASER MICRON
• Involuntary movement of the hand hinder the
  desired accuracy.
• Tremor (6-12 Hz 50µm pp)
• Jerk
• Drift

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Neurosurgery

• Surgeon try to burn cancerous tissues from the
  patients brain
• If all cancerous cells werent not removed, the
  tumors would grow up again
• If healthy cells were burnt, the patient life
  would be in danger

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Neuroarms

• Robots with 6 dof, stereo vision
• They are able to Working with a specialized set
  of tools.
• They are designed to perform soft tissue
  manipulation, needle insertion, blunt dissection,
  suturing, grasping of tissue, cauterizing,
  cutting, manipulation of a retractor, tool
  cleaning, suction and irrigation.

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But

• Sometimes surgeon remove the laser from the robot
  to end the work
• Other times is hard to program the robot to get
  the right orientation to burn the tumor
• The accuracy of this last operation depend on the
  tremor of the surgeon

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Vitreoretinal microsurgery

• Six degrees of freedom
• Three rotations
• Three translations
• The tip Point in the space ( 3 dof )
• ???
• ASAP

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Neurosurgery

• Four degrees of freedom
• Two rotations
• Two translations
• Laser tracking
• ???
• ?

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Options to solve the problem

• CCD camera
• Position sensing detector

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CCD camera

• High speed ( 100 fps )
• High accuracy ? High resolution
• Precision depend on the distance from the screen
• Very expensive system and very big system

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PSD

• Small (42mm x 29 mm)
• Easy to use (output proportional to position)
• -3dB Bandwidth 257 kHz
• Resolution (up to 0.25 µm)
• Linear (1full scale)
• Not need to focus

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First configuration
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Second configuration
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Intuitive idea
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Calculation of two angles
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Calculation of displacement






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General Scheme
Band pass Opt filter
PSD2
Beam splitter
AD card
Laser
Ch7
Laser
Ambient light
Alpha Beta Gx Gy
PSD1
X1
Transform microns into angles and positions
Subtract Offset
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Hardware
Power Inverse Bias
Position Sensing Detector 1
DATA output
Band pass Optical filter
Position Sensing Detector 2
Standard Cube Beam splitter
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Band pass optical filter

• Benefit eliminate most of the ambient light
• Type 10LF20-670
• C. Wavelength 667.3nm
• FWHM 19.4nm
• P. Transmission 53.1

10LF20-670, Newport, Irvine, CA
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Standard Cube Beamsplitter

• BS CUBE STANDARD 12.5MM TS
• Size 12.5mm x 12.5mm
• Reflection 50
• Transmission 50

NT45-111, Edmund optics, Barrington, NJ
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Position Sensing Detector

• 1 cm2 square PSD associated amplifier circuit.
• Voltage analog of the X,Y and spot intensity

DL 100- 7PCBA ,Pacific Silicon Sensor Inc.
,Westlake Village, CA
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First Result

• Only translation
• Calibration cross psd calibration (full range)
• Performance test (small steps)
• Only angle
• Calibration angle alpha
• Calibration angle beta
• Angle and translation
• Performance test
• Real tremor

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Before calibration

• Steps of 0.04 inch or 1mm

o target reading
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After calibration
o target reading
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Cross psd calibration
Max error x 20.08 µm Max error y 18.38
µm Range x 4000 µm Range y 4000
µm Linearity x 0.5 Linearity y 0.46
psd 2 psd 1
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Performance test

• Step of 2 mil or 50 micron

Max error x 5.0918 µm Max error y 5.7116
µm Range x 1016 µm Range y 1007
µm Linearity x 0.50 Linearity y 0.57
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Only angles
Wheel to reach different orientation of angle BETA
Wheel to reach different orientation of angle
ALPHA
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Angle (Alpha)
Range 2.5653 Maximum Error 0.0268 Linearity
1.04
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Angle (Beta)
Range 2.2526 Maximum Error 0.0517 Linearity
2.29
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Sensors noise at zero motion-angle
Standard derivation of error in alpha Std alpha
0.0022 8
Standard derivation of error in beta Std alpha
0.0022 8
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Sensors noise at zero motion-translation
Standard derivation of error in x translation Std
Gx error 4.1876 micron
Standard derivation of error in alpha Std Gy
error 4.0152 micron
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Real tremor (Rotation)
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Real tremor (translation)
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Future works

• Increase the workspace (bigger psds)
• Test other laser diode (reduce the noise)
• Determinate the distance between the filter and
  the laser in real time ( in study )
• Track surgeons tremor