non-destructive inspection with terahertz - lahat.com · zomega terahertz corporation - proprietary...

Zomega Terahertz Corporation - PROPRIETARY - DO NOT DISTRIBUTE WITHOUT PERMISSION

Non-destructive Inspection with Terahertz

March 25th 2014 Albert Redo-Sanchez

Zomega Terahertz Corporation 15 Tech Valley Drive, Suite 102

East Greenbush, NY 12061, USA

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Zomega Terahertz Corporation Focus

๏ Founded in 2005 to design, fabricate, and commercialize Terahertz systems and applications

๏ Core technology covered by seven patents issued and pending

๏ Only company that offers high data-rate, portable and handheld Terahertz systems

๏ Worldwide sales and service

๏ 40+ years of combined experience in Terahertz research and development

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Microwaves Visible X-ray γ-ray

Classic Theory(Electronics)

Quantum Theory(Photonics)

Frequency (Hz)

1 THz ~ 33 cm-1 ~ 1 ps ~ 300 um ~ 4 meV ~ 47 K

Terahertz

1015

Peta103

kilo106

Mega109

Giga1018

Exa1021

Zetta1024

Yotta1012

Tera

Radio IR

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Portfolio

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Components Auto-balanced detector, high-voltage modulators,

Photo-conductive antennas, ZAP detector...

Research Spectroscopy, Non-

destructive evaluation, Imaging, Plasma systems

Systems

Mini-Z, Micro-Z, FICO, ZAP, Z3


Differentiation

๏ Compact form factor systems ✓ Portable and handheld

✓ User-friendly, integrated

๏ High data rate ✓ Waveform rates up to 500 Hz

✓ Real-time and in-line inspection capabilities

๏ Open software plug-in architecture ✓ Integration with external systems and custom applications

๏ Detection based on Electro-Optic (EO) sampling ✓ More robust, broader bandwidth, and higher SNR than photo-conductive antennas

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Terahertz Technologies

Zomega’s Core Technology

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Terahertz Time-Domain Sources and Detectors

Sources

✓ Photoconductive Antennas (PCA)

✓ Optical Rectification

✓ Four-wave Mixing (Plasma)

✓ Surface Emitter (Photo-Dember)

✓ Tilted Wavefront (Cherenkov)

✓ Free-Electron Laser

Detectors

✓ Photoconductive Antennas

✓ Electro-Optical (EO) Sampling

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๏ Zomega builds its systems upon PCA as preferred emission mechanism and EO sampling as preferred detection mechanism

๏ ZAP (Zomega Air Photonics) system uses air plasma to generate and detect THz waves


EO Sampling vs. Photo-Conductive Antennas (detection)

Feature Photo-Conductive Antennas EO Sampling

ReliabilityVery sensitive to misalignment; gap

size ~10umLess sensitive to misalignment; laser beam

and THz overlap ~1 mm ➜ more robust

NoiseNon-differential method; laser noise

affects performanceDifferential method; noise is reduced more

effectively ➜ higher SNR

BandwidthTypically resonant devices;

Bandwidth is limited ~2 THzNon-resonant device;

Bandwidth >5 THz

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Terahertz Features

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๏ See-through ✓ Penetrates most non-metallic dry materials

๏ Pinpoint measurement and imaging ✓ Excellent spatial resolution (sub-mm)

๏ Molecular fingerprint ✓ Spectroscopic identification

๏ Safety ✓Non-ionizing radiation

๏ Non-contact ✓ Standoff emission/detection


Pulsed Terahertz Operation Modes

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๏ Non-destructive evaluation ✓ Cracks, voids, and other structural defects

✓ Thickness and coatings measurement

✓ Corrosion inspection

๏ Spectroscopy ✓ Pharmaceutical characterization and drug discovery

✓ Chemical and biological threat assessment

✓ Explosive detection


NDE Application Industries

๏ Automotive and Aeronautics

✓ Paint thickness and corrosion inspection on metal and composites

๏ Manufacturing

✓ Bonding in plastic components

✓ Composite structural defects

๏ Pharmaceutical

✓ Pill coatings thickness

✓ Pill integrity check

๏ Art inspection

✓ Authentication

✓ Style/technique research

✓ Restoration needs assessment

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Examples: Non-destructive Evaluation

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Textile materials

Foam materials

Internal structure

Corrosion under

insulation


Frequency Dependent Resolution

300 GHz 1 THz

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๏A broadband system contains many frequencies in the pulse

๏Resolution will depend on a particular frequency

๏Higher frequencies show better resolution (shorter wavelength)

Zomega Terahertz Corporation - PROPRIETARY - DO NOT DISTRIBUTE WITHOUT PERMISSIONZomega Terahertz Corporation - PROPRIETARY - DO NOT DISTRIBUTE WITHOUT PERMISSION

Analysis

๏ Waveform contains structure and spectroscopy data

✓ Complementary sets of data

๏ Multiple image analysis mode

✓ Amplitude (time-domain and frequency-domain), peak position, spectroscopy

๏ Layer analysis

✓ Roughness, topography

๏ Thin thicknesses (<50 um) require advanced data processing

✓ Waveform deconvolution

✓ Physical layer model fitting

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Why Terahertz for Thickness Measurements

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Ultrasound Inductive Terahertz

Strengths

• Sensitive sensors • Good resolution (>10 um) • Well stablished technology • Can separate different

layers

• Accurate and fast measurement

• Excellent resolution (~um)

• Good resolution (>10 um) • Can separate layers • Non-contact • Works on different substrates

(metal, ceramic, plastic, composite)

Weaknesses • Contact with sample

• Requires a metallic substrate • Cannot separate different

layers • Contact with sample

• Less developed technique • Coatings with metal content

may be challenging


Thickness Measurement Principle

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๏Each interface generates a pulse due to index of refraction mismatch

๏ Separation between pulses is directly related to the optical thickness (n*d)

๏ Simplified model assumes:

✓ Index of refraction is constant across the bandwidth of the pulse

✓ Thickness measured is smaller than depth of focus


Plastic Components

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๏Adhesive between slabs cannot be seen in non-optically transparent plastics

๏ IR cannot penetrate and detect presence/absence of adhesive

๏B-scans allows studying the layered structure of the sample and measure thicknesses

Front slab measured thickness 1.279 mm

Nominal thickness 1.320 mm

Discrepancy -3%

Back slab measured thickness 1.294 mm


Discrepancy -2%

Measured inner interface 0.294 mm


Discrepancy 1%


Pharmaceutical Coatings

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Meas.: 22-24 um Nom.: 15-30 um Disc.: within interval

Meas.: 115 um Nom.: 120 um Disc.: 4%


Tera Art

๏ Papyrus

๏ Mural paintings

๏ Pottery

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Labaune, J., Jackson, J. B., Pagès-Camagna, S., Duling, I. N., Menu, M., & Mourou, G. A. (2010). Papyrus imaging with terahertz time domain spectroscopy. Applied Physics A, 100(3), 607–612. Jackson, J. B., Mourou, M., Whitaker, J. F., Duling, I. N., Williamson, S. L., Menu, M., & Mourou, G. A. (2008). Terahertz imaging for non-destructive evaluation of mural paintings. Optics Communications, 281(4), 527–532. Caumes, J.-P., Younus, A., Salort, S., Chassagne, B., Recur, B., Ziéglé, A., et al. (2011). Terahertz tomographic imaging of XVIIIth Dynasty Egyptian sealed pottery. Applied Optics, 50(20), 3604–3608.


Why Terahertz for Art Inspection

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X-ray Infrared Terahertz

Strengths• Highest penetration • Highest resolution • Fast (cameras available)

• Excellent resolution • Fast (cameras available) • Non-hazardous

• Can penetrate deep into the sample (~mm)

• Sensitivity to molecular composition

• Layer analysis • Non-hazardous

Weaknesses

• Cannot discriminate compounds with similar atomic weight

• Hazardous

• Only penetrates few um into the sample (no depth data)

• No layer structure information• Slow (single pixel acquisition)


Finding Goya: “Sacrifice to Vesta” (1771)

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X-ray image does not show too much structural information


Data Acquisition Considerations

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๏Each pixel contains depth/frequency data

✓ Data is not flat but a cube (stack)

✓ Data files can be very big

๏ Size is 33 x 24 cm

๏Tiling

✓ Thickness measured is smaller than depth of focus

๏ Stitching

✓ Analyze each section separately and stitch final results


Art Inspection

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๏ Feature that resembles the signature of the artist can be seen in the THz image

๏ This feature cannot be seen in X-ray images

๏ IR may only see features that are nearby surface (<20 um) but not deep features like this one (>100 um)

Seco-Martorell, C., López-Domínguez, V., Arauz-Garofalo, G., Redo-Sanchez, A., Palacios, J., & Tejada, J. (2013). Goya’s artwork imaging with Terahertz waves. Optics Express, 21(15), 17800. doi:10.1364/OE.21.017800


Fiber-Coupled (FiCO) THz Time-Domain System

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Benefits ๏ High experimental flexibility

๏ Multiple applications

๏ Real-time, fast measurements

Features ๏ Independent emitter and receiver heads

๏ Broad bandwidth or high sensitivity selectable

๏ Waveform rate of 500 Hz

๏ Several lens options

๏ Transmission, normal and pitch-catch reflection

๏ Expandable and customizable software (open source)

Options ๏ High speed imaging

๏ θ-2θ reflection

๏ ATR

๏ Compatible with cryostat


Mini-Z Terahertz Time-Domain Spectrometer

Benefits ๏ Portable, quick, and easy to setup

๏ Turn-key operation

๏ Stable and reliable

๏ Real-time, fast measurements

Features ๏ Integrated and compact design

๏ Broadband sensitivity up to 3.5 THz and high dynamic range >70 dB

๏ Modular transmission and reflection geometries

๏ Waveform rate up to 500 Hz (high speed model)

๏ Vibration tolerant

๏ Purgeable

๏ Expandable and customizable software (open source)

Options ๏ High speed imaging

๏ θ-2θ reflection

๏ ATR

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Summary

๏ Terahertz provides structural information complementary to other technologies

๏ Time of flight data can be used to measure thickness of layers

๏ Software (data analysis) is as important as hardware in order to implement an application

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Thank You!

Zomega Terahertz Corporation 15 Tech Valley Drive

East Greenbush, NY 12061 (USA) !

Web: www.z-thz.com E-mail: [email protected] Phone: +1-518-833-0577

Questions?

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http://www.z-thz.com

mailto:[email protected]

non-destructive inspection with terahertz - lahat.com · zomega terahertz corporation - proprietary...

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