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MADRIDMeasurement Apparatus to Distinguish Rotational and Irrotational Displacement

Rafael OrtizGraduate student

Universidad de Valladolid (Spain)

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MADRID

Problem to solve Reasons of choosing this option Description of the device First result Conclusion

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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 Jerk Drift

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Vitreoretinal microsurgery

Five degree of freedom Two rotation Three translation

Tip tracking

↓↓↓

ASAP

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Vitreoretinal microsurgery

Four degree of freedom Two rotation Two translation

Laser tracking

↓↓↓

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Options to solve the problem

Gyros.

CCD camera

MADRID

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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

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CCD camera

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

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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

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21arctan

AA

BB

A1 A2

B1

B2

Point 1

Point 2

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3D problem

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Configuration

Position SensingDetector #1

Position SensingDetector #2

DATAoutput

PowerInverse Bias

Band pass Optical filter

Standard Cube Beam splitter

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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

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Laser Diode

Focusable Laser Features:

CWWavelengths670nm ±10nm,

DiameterLDM, Circular: 5mm; 

Focus Range LDM, Circular: 150mm to Infinity; 

NT38-920,Edmund optics, Barrington, NJ

0.5m 1m 2m 5m

<0.5 <0.5 <1 1

Spot Size (mm) at DistanceSpot Size (mm) at Distance

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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 analogd of the X,Y and spot intensity

Reverse Bias is applied

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

Sum(y)Ch7V(y)Ch6

Sum(x)Ch5V(x)Ch4PSD #2

Sum(y)Ch3V(y)Ch2

Sum(x)Ch1V(x)Ch0PSD #1

FormulaMeaningChannel

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11 ChChAx

32

11 ChChBy

54

22 ChChAx

76

22 ChChBy

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Calculation of two angles

da

xxArc 21tan

da

yyArc 21tan

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Calculation of displacement

tan1 cbaxg x

tan1 cbayg y

tan2 cbdxg x

tan2 cbdyg y

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General Scheme

Ch6Ch5Ch4

Ch3Ch2Ch1Ch0

FilterBand pass

Cutoff 22Hz

Y1

X2

Y2

Transform volts into microns

Laser

Ambient light

Band pass Opt filter

Laser

Beam splitter

Ch7

ADcard

PSD#1

PSD#2

Subtract Offset

Transform microns into angles and

positions

X1

Alpha Beta

Gx Gy

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First Result

Different modes Only translation Only angle Angle and translation

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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)

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Full Range (only translation)

-2500 -2000 -1500 -1000 -500 0 500 1000 1500 2000 2500-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500Final PSD1 & PSD2 in micron

Xaxis(micron)

Yax

is(m

icro

n)

8.7268

6.4684

-0.0058

-0.0058

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Small Step

6.7942

4.0104

-8.8044

-2.1234

-600 -500 -400 -300 -200 -100 0 100 200 300 400 500 600-600

-500

-400

-300

-200

-100

0

100

200

300

400

500

600

X axis(microns)

Y a

xis(

mic

rons

)

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Only angles

Wheel to reach different orientation

of angle ALPHA

Wheel to reach different orientation

of angle BETA

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Angle (Alpha)

0 5 10 15 20 25 30 35 40 45-1.5

-1

-0.5

0

0.5

1

1.5

Set of data

Alp

ha(D

egre

es)

Real measurment of angleReading with MADADError

Error

Range =2.5653°

Maximum Error 0.0268 °

Linearity =1.04%

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Angle (Beta)

0 5 10 15 20 25-1.5

-1

-0.5

0

0.5

1

Set of data

Bet

a(D

egre

es)

Real measurement of angleReading with MADADError

Range =2.2526°

Maximum Error 0.0517°

Linearity =2.29%

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Angle in completed mode

0 500 1000 1500 2000 2500 3000 3500 4000 4500-0.035

-0.03

-0.025

-0.02

time(millisecond)

Rot

atio

n A

lpha

(deg

ree)

0 500 1000 1500 2000 2500 3000 3500 4000 45000.41

0.415

0.42

0.425

0.43

time(millisecond)

Rot

atio

n B

eta(

degr

ee)

Standard derivation of error

in alphaStd alpha

0.0022° ≈ 8’’

Standard derivation of error

in betaStd alpha

0.0022° ≈ 8’’

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Translation in completed mode

0 500 1000 1500 2000 2500 3000 3500 4000 45001135

1140

1145

1150

1155

1160

1165

time(millisecond)

Pos

ition

Gx

(mic

ron)

0 500 1000 1500 2000 2500 3000 3500 4000 4500125

130

135

140

145

150

time(millisecond)

Pos

ition

Gy(

mic

ron)

Standard derivation of error

in x translationStd Gx error

4.1876 micron

Standard derivation of error

in alphaStd Gy error

4.0152 micron

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Real tremor (Rotation)

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000-2.5

-2

-1.5

-1

time (millisecond)

rota

tion

alph

a (d

egre

e)

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000-4.6

-4.4

-4.2

-4

-3.8

time (millisecond)

rota

tion

beta

(de

gree

)

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Real tremor (translation)

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100004000

4500

5000

5500

6000

6500

7000

time(millisecond)

tran

slat

ion

gx (

mic

ron)

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100007500

8000

8500

9000

9500

10000

10500

time (millisecond)

tran

slat

ion

gy (

mic

ron)

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Conclusion