MADRID Measurement Apparatus to Distinguish Rotational and Irrotational Displacement

1
MADRIDMeasurement 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

Point 1
Point 2
10
3D problem
11
Configuration
Power Inverse Bias
Position Sensing Detector 1
DATA output
Band pass Optical filter
Position Sensing Detector 2
Standard Cube Beam splitter
12
Bandpass 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
13
Laser Diode

• Focusable Laser
• Features
• CWWavelengths670nm 10nm,
• DiameterLDM, Circular 5mm 
• Focus Range LDM, Circular 150mm to Infinity 

Spot Size (mm) at Distance
0.5m 1m 2m 5m
lt0.5 lt0.5 lt1 1
NT38-920,Edmund optics, Barrington, NJ
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 cm2 square PSD associated amplifier circuit.
• Voltage analogd of the X,Y and spot intensity
• Reverse Bias is applied

DL 100- 7PCBA ,Pacific Silicon Sensor Inc.
,Westlake Village, CA
16
Calculation of two angles
17
Calculation of displacement






18
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
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)
8.7268 6.4684 -0.0058 -0.0058
22
Small Step
6.7942 4.0104 -8.8044 -2.1234
23
Only angles
Wheel to reach different orientation of angle BETA
Wheel to reach different orientation of angle
ALPHA
24
Angle (Alpha)
Range 2.5653 Maximum Error 0.0268 Linearity
1.04
25
Angle (Beta)
Range 2.2526 Maximum Error 0.0517 Linearity
2.29
26
Angle in completed mode
Standard derivation of error in alpha Std alpha
0.0022 8
Standard derivation of error in beta Std alpha
0.0022 8
27
Translation in completed mode
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
28
Real tremor (Rotation)
29
Real tremor (translation)
30
Conclusion