S. Mandayam, ECE Dept., Rowan University

Parametric Characterization of Parametric Characterization of PSF of Split-D Core EC ProbesPSF of Split-D Core EC ProbesParametric Characterization of Parametric Characterization of PSF of Split-D Core EC ProbesPSF of Split-D Core EC Probes

Department of Electrical & Computer Engineering

201 Mullica Hill RoadGlassboro, NJ 08028, USA

engineering.rowan.edu

Shreekanth MandayamShreekanth Mandayam

GE John F. Welch Technology CenterBangalore, India

S. Mandayam, ECE Dept., Rowan University

OutlineOutline• Objectives

• Approach– Parametric PSF Model– EC Signature Deconvolution

• Pre-Restoration Filtering

• Results– Simulated Image Template– SC EC Images

• Summary

S. Mandayam, ECE Dept., Rowan University

ObjectivesObjectives

• To design and develop a numerical parametric model for multiple EC probe PSFs

• To validate parametric PSF model by deconvolution of EC signatures for flaw characterization

S. Mandayam, ECE Dept., Rowan University

Experimental Data (GEMTC)Experimental Data (GEMTC)

• SGE638 and SGE596 split-D core EC probes• EC-2000 system at 6-MHz• Copper wire (200-mils diameter) tip sharpened to

3-mil diameter embedded in 1” thick hard polystyrene foam.

• Ferrous tip• 500 x 500 TIFF files with a pixel resolution of 1-

mil x 1-mil

S. Mandayam, ECE Dept., Rowan University

Experimental Data (GEMTC)Experimental Data (GEMTC)

Cu Tip Fe Tip SGE638

S. Mandayam, ECE Dept., Rowan University

Parametric PSF Model (1-DOF)Parametric PSF Model (1-DOF)

2

22

2

)(

),( yx

eyxg

yyxpxyxqyyxgy

xyxgx

yxg ˆ),(ˆ),(ˆ),(ˆ),(),(

S. Mandayam, ECE Dept., Rowan University

Parametric PSF Model (2-DOF)Parametric PSF Model (2-DOF)

2

2

2

2

22),( yx

yx

eeyxg

),(ˆ).,(),( yxgy

yyxgyxp

S. Mandayam, ECE Dept., Rowan University

Parametric PSF Model (2-DOF)Parametric PSF Model (2-DOF)  PSF

Size

mils

mils

mils

SGE638 – Cu tip

44 x 42 19.802 11.002

SGE638 – Fe tip

51 x 43 17.852 12.752

SGE596 – Cu tip

121 x 36 12.102 32.672

SGE596 – Fe tip

109 x 31 10.92 32.702

2y2

x

S. Mandayam, ECE Dept., Rowan University

PSF: Fe Tip PSF Model

0

50

02040600

0.5

1

Comparison

0 20 40 600

0.2

0.4

0.6

0.8

1

Experimental

Model

SGE638

S. Mandayam, ECE Dept., Rowan University

PSF: Cu Tip PSF Model

0

50

02040600

0.5

1

Comparison

0 20 40 600

0.2

0.4

0.6

0.8

1

Experimental

Model

SGE638

S. Mandayam, ECE Dept., Rowan University

PSF: Cu Tip, SGE596 PSF Model

0

20

40

0501001500

0.5

1

Comparison

0 50 100 1500

0.2

0.4

0.6

0.8

1

Experimental

Model

SGE596

S. Mandayam, ECE Dept., Rowan University

PSF: Fe Tip, SGE596 PSF Model

020

40

0501001500

0.5

1

Comparison

0 50 100 1500

0.2

0.4

0.6

0.8

1

Experimental

Model

SGE596

S. Mandayam, ECE Dept., Rowan University

EC Signature DeconvolutionEC Signature Deconvolution

: Probe PSF model : Eddy-current inspection signature

: Deconvolved image (defect/flaw profile)

),( yxp ),( vuP

),( yxs ),( vuS

),( yxd ),( vuD

),(),(),(

),(*),(),(

vuPvuDvuS

yxpyxdyxs

S. Mandayam, ECE Dept., Rowan University

Deconvolution MethodsDeconvolution Methods

Lucy-Richardson Algorithm

),(),(),(),(

),(),(1 yxdyxp

yxpyxdyxs

yxd ii

i

Wiener Filter

),(

),(),(),(

),(),(ˆ

2

*vuS

vuSvuSvuP

vuPvuD

ddnn

S. Mandayam, ECE Dept., Rowan University

Simulated Image Template: Simulated Image Template: Effect of Anisotropic PSFEffect of Anisotropic PSF

Slot Template

d(x,y) * p(x,y) = s(x,y)

Wiener Lucy-Rich.

S. Mandayam, ECE Dept., Rowan University

Simulated Image Template: Simulated Image Template: Effect of Isotropic PSFEffect of Isotropic PSF

Slot Template

d(x,y) * p(x,y) = s(x,y)

Wiener Lucy-Rich.

Blurred

Wiener Restored

Lucy-Richardson Restored

S. Mandayam, ECE Dept., Rowan University

Pre-Restoration FilterPre-Restoration Filter

),(),(),( yxpyxdyxs

),(),(),( yxfyxsyxs f

),(),(),( yxhyxfyxp

),(),(),( yxhyxdyxs f

Anisotropic PSF

Pre-restoration filter

Isotropic PSF

Isotropic blur

S. Mandayam, ECE Dept., Rowan University

Results: Simulated ImageResults: Simulated ImageSlot Template PSF Model: Grad(Gaussian)

Blurred

BlurredPre-Restoration Filter Pre-Filtered

Restoration PSFPSF Model: Grad(Gaussian) Pre-Restoration Filter

Lucy-Richardson Restored

d(x,y) * p(x,y) = s(x,y)

s(x,y) * f(x,y) = sf(x,y)

p(x,y) * f(x,y) = h(x,y)

L-C Restored

Anisotropic PSF

Pre-restorationfilter

Isotropic blur

IsotropicPSF

S. Mandayam, ECE Dept., Rowan University

Simulated Image; Simulated Image; Experimental PSFExperimental PSF

Blurred Cu TipPre-Filter Cu Tip Restoration PSF Cu Tip

Lucy-Richardson Restored: Cu Tip

s(x,y) p(x,y) f(x,y) h(x,y)

L-CRestored

PSF: Cu Tip

S. Mandayam, ECE Dept., Rowan University

SC-EC Images on DatabaseSC-EC Images on Databaseiimlgeaenge$ on 'bng1nas02.jfwtc.ge.com‘

DA718_H01_163S/DA718_H01_163S.S.1.030504.1459

EC Signature Binary

Original RestoredEC Signature Binary

S. Mandayam, ECE Dept., Rowan University

SC-EC Images on DatabaseSC-EC Images on Databaseiimlgeaenge$ on 'bng1nas02.jfwtc.ge.com‘

DA718_H01_163S/DA718_H01_163S.S.2.030504.1459

Original Restored

EC Signature Binary

EC Signature Binary

S. Mandayam, ECE Dept., Rowan University

SummarySummary

• Parametric model for PSF of split-D core EC Probe

• Deconvolution algorithm to compensate for anisotropic probe PSF