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 Conclusion

3 Introduction High accuracy in microsurgery Vitreoretinal microsurgery  MICRON Neurosurgery  LASER MICRON Involuntary movement of the hand hinder the desired accuracy. Tremor Jerk Drift

4 Vitreoretinal microsurgery Five degree of freedom Two rotation Three translation Tip tracking ↓↓↓ ASAP

5 Vitreoretinal microsurgery Four degree of freedom Two rotation Two translation Laser tracking ↓↓↓ 

6 Options to solve the problem Gyros. CCD camera MADRID

7 Use a par of gyros Translation information is missing Device should be useful for laser micron calibration. Impossible to set a gyros above a laser ray

8 CCD camera High speed ( 100 fps ) High accuracy ↔ High resolution Very expensive system

9 MADRID First idea: Only two dots are required to draw a line. If the laser is tracking in two different positions, the angle may be calculated A1A2 B1 B2  Point 1 Point 2

10 3D problem

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

12 Bandpass 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

13 Laser Diode Focusable Laser Features:  CWWavelengths670n m ±10nm,  DiameterLDM, Circular: 5mm;  Focus Range LDM, Circular: 150mm to Infinity; NT38-920,Edmund optics, Barrington, NJ 0.5m1m2m5m <0.5 <11 Spot Size (mm) at Distance

14 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

15 Position Sensing Detector 1 cm 2 square PSD & associated amplifier circuit. Voltage analogd of the X,Y and spot intensity Reverse Bias is applied DL PCBA,Pacific Silicon Sensor Inc.,Westlake Village, CA Sum(y)Ch7 V(y)Ch6 Sum(x)Ch5 V(x)Ch4 PSD #2 Sum(y)Ch3 V(y)Ch2 Sum(x)Ch1 V(x)Ch0 PSD #1 FormulaMeaningChannel

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

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

18 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

19 First Result Different modes Only translation Only angle Angle and translation

20 Only translation Redundant data (alpha and beta must be null) Two studies Full Range (step 0.04 inch or 1mm) Small step (step 2 mil or 50 micron)

21 Full Range (only translation)

22 Small Step

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

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

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

26 Angle in completed mode Standard derivation of error in alpha Std alpha ° ≈ 8’’ Standard derivation of error in beta Std alpha ° ≈ 8’’

27 Translation in completed mode Standard derivation of error in x translation Std Gx error micron Standard derivation of error in alpha Std Gy error micron

28 Real tremor (Rotation)

29 Real tremor (translation)

30 Conclusion