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

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

3 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

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

5 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.

6 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

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

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

9 Options to solve the problem CCD camera Position sensing detector

10 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

11 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

12 First configuration

13 Second configuration

14 Intuitive idea

15 Calculation of two angles          da xx Arc 21 tan           da yy Arc 21 tan 

16 Calculation of displacement   tan1cbaxg x    1cbayg y    2cbdxg x    2cbdyg y 

17 General Scheme Ch6 Ch5 Ch4 Ch3 Ch2 Ch1 Ch0 Filter Band pass Cutoff 22Hz Y 1 X 2 Y 2 Transform volts into microns Laser Ambient light Band pass Opt filter Laser Beam splitter Ch7 AD card PSD#1 PSD#2 Subtract Offset Transform microns into angles and positions X 1 Alpha Beta Gx Gy

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

19 Band pass optical filter Benefit: eliminate most of the ambient light Type: 10LF  C. Wavelength: 667.3nm  FWHM: 19.4nm  P. Transmission: 53.1% 10LF20-670, Newport, Irvine, CA

20 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

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

22 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

23 Before calibration o target + reading Steps of 0.04 inch or 1mm

24 After calibration o target + reading

25 Cross psd calibration Max error x = μm Max error y = μm Range x = 4000 μm Range y = 4000 μm Linearity x = 0.5% Linearity y = 0.46% + psd #2 + psd #1

26 Performance test Max error x = μm Max error y = μm Range x = 1016 μm Range y = 1007 μm Linearity x = 0.50% Linearity y = 0.57% Step of 2 mil or 50 micron

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

28 Angle (Alpha) Range =2.5653° Maximum Error ° Linearity =1.04%

29 Angle (Beta) Range =2.2526° Maximum Error ° Linearity =2.29%

30 Sensors noise at zero motion-angle Standard derivation of error in alpha Std alpha ° ≈ 8’’ Standard derivation of error in beta Std alpha ° ≈ 8’’

31 Sensors noise at zero motion- translation Standard derivation of error in x translation Std Gx error micron Standard derivation of error in alpha Std Gy error micron

32 Real tremor (Rotation)

33 Real tremor (translation)

34 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 surgeon’s tremor