microwave imaging using indirect synthetic reference beam holography dr. m. elsdon ceis, northumbria...
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Microwave Imaging using Indirect Microwave Imaging using Indirect Synthetic Reference Beam Synthetic Reference Beam
Holography Holography
Dr. M. Elsdon
CEIS, Northumbria University, Newcastle-upon-Tyne, NE1 8ST, UK
Presentation to Calgary University - October 2005
IntroductionIntroduction
Overview of Northumbria University Imaging Group
Overview of Holographic Imaging
Describe Northumbria University’s Imaging Technique – Indirect Holography
Applications of this technique:
Antenna fields
Concealed Metal Objects
Dielectric Objects,
Breast Cancer Detection
ABOUT MEABOUT ME
Dr. Michael Elsdon
BEng (Hons) Electronic and Communication Engineering
PhD ‘Compact Microstrip Antennas’
July 2005: Post-Doctoral Researcher
Microwave Imaging Research Group, Northumbria University, UK
Project: ‘Microwave Imaging of Breast Cancer’
Research OverviewResearch Overview
Work of group based upon patented invention of Northumbria Work of group based upon patented invention of Northumbria University: ‘Synthetic Reference Beam Holography’University: ‘Synthetic Reference Beam Holography’
Exploits the advantage of NOT requiring direct Exploits the advantage of NOT requiring direct measurement of phase. measurement of phase.
Mathematical Reconstruction enables phase to be Mathematical Reconstruction enables phase to be ‘deduced’‘deduced’
VNA replaced with Diode Detector – LOW COSTVNA replaced with Diode Detector – LOW COST
Applications: Applications:
Antenna Radiation Pattern MeasurementAntenna Radiation Pattern Measurement
Airport SecurityAirport Security
Medical ImagingMedical Imaging
Holographic Approach For ImagingHolographic Approach For Imaging
1. DIRECT HOLOGRAPHY:
Measure amplitude and phase of scattered signal
Reconstruct Image using Mathematical Techniques
Requires VNA - EXPENSIVE
VectorNetworkAnalyser
PositionControl
SamplingAntennasObject
Tx
Rx
2. INDIRECT HOLOGRAPHY:
3D Images can be reconstructed from Amplitude of scattered signal Requires only SCALAR measurements
Requires Only Simple Diode Detector
- INEXPENSIVE
Indirect HolographyIndirect Holography
Two Stage Process:Two Stage Process:
Stage 1:Stage 1:
Illuminate Object with reference wave to Illuminate Object with reference wave to form Hologram (Intensity Pattern)form Hologram (Intensity Pattern)
Stage 2:Stage 2:
Reconstruct Image of Original Object Reconstruct Image of Original Object using post-processing softwareusing post-processing software
Stage 1: Formation of Intensity PatternStage 1: Formation of Intensity Pattern
Illuminate object with coherent reference Illuminate object with coherent reference wavewave
Combine reflected signal with reference Combine reflected signal with reference signalsignal
Form Intensity Pattern – HologramForm Intensity Pattern – Hologram
Record Intensity of HologramRecord Intensity of Hologram
Intensity Pattern Formation – Intensity Pattern Formation – Experimental Arrangement for Data CollectionExperimental Arrangement for Data Collection
Object
RX ProbeRX Probe
Controller
TX ProbeTX ProbePower Meter
Intensity PatternI (x,y)
MicrowaveSource
DirectionalCoupler
Variable Attenuator
Phase Shifter
PositionControl
SyntheticSyntheticReference Reference
WaveWave
HybridTee
Stage 2: Image ReconstructionStage 2: Image Reconstruction
Take Fourier Transform of Recorded Take Fourier Transform of Recorded Intensity PatternIntensity Pattern
Filter Fourier Transform to remove Filter Fourier Transform to remove unwanted termsunwanted terms
Take Inverse Fourier TransformTake Inverse Fourier Transform
Perform Back-propagation and IFT to Perform Back-propagation and IFT to produce image at selected depthproduce image at selected depth
1. Intensity Pattern
2. Fourier Transform
22),(),(),( yxRFyxEFyxIF ),(),(),(),( yxRFyxEFyxRFyxEF
+Xm-Xm
+km-Km-Km +km
Direct Wave
Image 2Image 1
2),(),(),( yxRyxEyxI
kx
ky
Required Term
Spectral Representation of Off-axis Hologram:
Synthesized Reference Wave separates required term from origin
Problem:Problem: Difficult to produce sufficient offset to separate terms of Fourier Transform
3. Filter off Unwanted Terms
4. Re-centre remaining term
+km-Km-Km +km
Direct Wave
Image 2Image 1
Measurement Plane Image
+km-Km
Image 2
5. Back-propagate to selected depth and perform IFT
ORIGINAL IMAGE ORIGINAL IMAGE
At Object PlaneAt Object Plane
+km-Km
Image 2
History of Microwave Imaging History of Microwave Imaging Research at NorthumbriaResearch at Northumbria
1. Imaging of Antenna Radiation Characteristics
2. Imaging of Concealed Metal Objects
3. Imaging of Plastic Objects
4. Breast Cancer Detection
1. Antenna Radiation Characteristics1. Antenna Radiation Characteristics
Microwave SourceVariable
Attenuator
Phase Shifter
Microwavemixer andDetector
P.C
Antenna underTest
A.U.T.Data
Output
Parabolic Dish Data Collection System
Reconstructed Near-Field
Magnitude Phase
2. Imaging of Concealed Metal Objects
Uncovered Triangle: Triangle Covered with Cloth:
Intensity Pattern Formation – Intensity Pattern Formation – Experimental Arrangement for Data CollectionExperimental Arrangement for Data Collection
Object
RX ProbeRX Probe
Controller
TX ProbeTX ProbePower Meter
Intensity PatternI (x,y)
MicrowaveSource
DirectionalCoupler
Variable Attenuator
Phase Shifter
PositionControl
SyntheticSyntheticReference Reference
WaveWave
HybridTee
Typical Intensity PatternTypical Intensity Pattern
Linear Phase Shift Applied to Synthetic Reference Wave
240120024012002401200
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240120024012002401200
240120024012002401200
240120024012002401200
240120024012002401200
240120024012002401200
Plane Wave Spectrum
Reconstructed IMAGEReconstructed IMAGE
Problem of Previous Example:Problem of Previous Example:
Terms in PWS overlap if object is tilted, can’t separate terms
Can only image objects that are FLAT
kx
ky
+ve xTILT
+ve xTILT
-ve xTILT
-ve xTILT
-ve yTILT
-ve yTILT
+ve yTILT
+ve yTILT
SOLUTION:SOLUTION:
Apply 2D phase shift to reference wave
12002401201202401200240
024012002401200240120
240120024012002401200
120024012002401200240
024012002401200240120
240120024012002401200
120024012002401200240
024012002401200240120
240120024012002401200
kx
ky
+ve xTILT
+ve xTILT
-ve xTILT
-ve xTILT
-ve yTILT
-ve yTILT
+ve yTILT
+ve yTILT
PWS with 2D Phase Shift
Tilted Objects do not cause terms to overlap
3. Imaging of Dielectric Objects3. Imaging of Dielectric Objects
Recorded Intensity Pattern
F.T of Intensity Pattern
Reconstructed IMAGEReconstructed IMAGE
4. Imaging of Breast Cancer - Crude Phantom4. Imaging of Breast Cancer - Crude Phantom
Illum
inat
ing
Ante
nna
Rece
ivin
gAn
tenn
a
h
d1Tumor
1r
ImmersionMedium
2r
εr1 = 30, εr2 = 2, d1 = 35mm, h = 10cm, x = y = 40cm, dx = dy = 1cm, f = 8.6GHz
Photo of Breast PhantomPhoto of Breast Phantom
Photo of Experimental SetupPhoto of Experimental Setup
Recorded Intensity Pattern
F.T of Intensity Pattern
Reconstructed IMAGEReconstructed IMAGE
Benefits of Northumbria University’s TechniqueBenefits of Northumbria University’s Technique
Provides 3D Holographic Image from “Single –Provides 3D Holographic Image from “Single –View” 2D ScanView” 2D Scan
Employs Patented Employs Patented SyntheticSynthetic Reference Beam Reference Beam ElectronicallyElectronically Hologram “Created” in SoftwareHologram “Created” in Software
Compact Microwave Network Compared to External Compact Microwave Network Compared to External Offset Reference Beam Antenna GeometryOffset Reference Beam Antenna Geometry
Low-CostLow-Cost Simple Square-Law Detector in Lieu of Vector Simple Square-Law Detector in Lieu of Vector
AnalyserAnalyser
Phase Retrieval via Mathematical Reconstruction Phase Retrieval via Mathematical Reconstruction ProcessProcess
Dr David SmithDr David Smith, Team Leader & Inventor of , Team Leader & Inventor of Synthetic Reference Beam Holography Synthetic Reference Beam Holography
Dr Michael ElsdonDr Michael Elsdon, Post - Doctoral Researcher, Post - Doctoral Researcher
Dr Mark LeachDr Mark Leach, Post - Doctoral Researcher, Post - Doctoral Researcher
Prof. Stephen J FotiProf. Stephen J Foti, Consultant, Consultant
MrMr M. JoyM. Joy, PhD Student, PhD Student
Microwave Imaging Research Group Microwave Imaging Research Group Northumbria UniversityNorthumbria University
AcknowledgementsAcknowledgements
Engineering and Physical Science Research CouncilEngineering and Physical Science Research Council
(EPSRC)(EPSRC)
Wellcome TrustWellcome Trust
Newcastle University Medical SchoolNewcastle University Medical School
Prof. T. Lennard Prof. T. Lennard (Royal Victoria Infirmary)(Royal Victoria Infirmary)
Mr Peter ElsdonMr Peter Elsdon, Technical Consultant, Technical Consultant
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