MADRID Measurement Apparatus to Distinguish Rotational and Irrotational

MADRID Measurement Apparatus to Distinguish Rotational and Irrotational Displacement Rafael Ortiz Graduate student Universidad de Valladolid (Spain) 1

MADRID n Problem to solve n Reasons of choosing this option n Description of the device n First result n Future works 2

Introduction n High accuracy in microsurgery • • Vitreoretinal microsurgery MICRON Neurosurgery LASER MICRON n Involuntary movement of the hand hinder the desired accuracy. n n n Tremor (6 -12 Hz 50μm pp) Jerk Drift 3

Neurosurgery n Surgeon try to burn cancerous tissues from the patient’s brain n If all cancerous cells weren’t not removed, the tumors would grow up again n If healthy cells were burnt, the patient life would be in danger 4

Neuroarms n Robots with 6 dof, stereo vision n They are able to Working with a specialized set of tools. n 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. 5

But … n Sometimes surgeon remove the laser from the robot to end the work n Other times is hard to program the robot to get the right orientation to burn the tumor n The accuracy of this last operation depend on the tremor of the surgeon 6

Vitreoretinal microsurgery n Six degrees of freedom n Three rotations n Three translations n The tip ≈ Point in the space ( 3 dof ) ↓↓↓ ASAP 7

Neurosurgery n Four degrees of freedom n n Two rotations Two translations n Laser tracking ↓↓↓ 8

Options to solve the problem n. CCD camera n. Position sensing detector 9

CCD camera n High speed ( 100 fps ) n High accuracy ↔ High resolution n Precision depend on the distance from the screen n Very expensive system and very big system 10

PSD n Small (42 mm x 29 mm) n Easy to use (output proportional to position) n -3 d. B Bandwidth: 257 k. Hz n Resolution (up to 0. 25 μm) n Linear (± 1 full scale) n Not need to focus 11

First configuration 12

Second configuration 13

Intuitive idea 14

Calculation of two angles æ x 1 - x 2 ö a = Arc tan ç ÷ è a-d ø æ y 1 - y 2 ö b = Arc tan ç ÷ è a-d ø 15

Calculation of displacement g x = x 1 - (a + b + c )tan (a ) g y = y 1 - (a + b + c )tan (b ) g x = x 2 - (d + b + c )tan (a ) g y = y 2 - (d + b + c )tan (b ) 16

General Scheme Laser Band pass Opt filter Beam splitter PSD#2 Ch 7 Ch 6 Ch 5 Ch 4 Laser Ambient light Alpha Beta Gx Gy PSD#1 Ch 3 Ch 2 Ch 1 Ch 0 AD card X 1 Transform microns into angles and positions Y 1 X 2 Y 2 Transform volts into microns Filter Band pass Cutoff 22 Hz Subtract Offset 17

Hardware Position Sensing Detector #1 Power Inverse Bias DATA output Band pass Optical filter Standard Cube Beam splitter Position Sensing Detector #2 18

Band pass optical filter n n Benefit: eliminate most of the ambient light Type: 10 LF 20 -670 C. Wavelength: 667. 3 nm FWHM: 19. 4 nm P. Transmission: 53. 1% 10 LF 20 -670, Newport, Irvine, CA 19

Standard Cube Beamsplitter n BS CUBE STANDARD 12. 5 MM TS n Size: 12. 5 mm x 12. 5 mm n Reflection : 50 % n Transmission : 50 % NT 45 -111, Edmund optics, Barrington, NJ 20

Position Sensing Detector n 1 cm 2 square PSD & associated amplifier circuit. n Voltage analog of the X, Y and spot intensity DL 100 - 7 PCBA , Pacific Silicon Sensor Inc. , Westlake Village, CA 21

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 22

Before calibration n. Steps of 0. 04 inch or 1 mm o target + reading 23

After calibration o target + reading 24

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 25

Performance test n. 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% 26

Only angles Wheel to reach different orientation of angle BETA Wheel to reach different orientation of angle ALPHA 27

Angle (Alpha) Range =2. 5653° Maximum Error 0. 0268 ° Linearity =1. 04% 28

Angle (Beta) Range =2. 2526° Maximum Error 0. 0517° Linearity =2. 29% 29

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’’ 30

Sensors noise at zero motiontranslation 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 31

Real tremor (Rotation) 32

Real tremor (translation) 33

Future works n Increase the workspace (bigger psds) n Test other laser diode (reduce the noise) n Determinate the distance between the filter and the laser in real time ( in study ) n Track surgeon’s tremor 34