Non-destructive Inspection with Terahertz

Transcription

1 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!1

2 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 Classic Theory (Electronics) Terahertz Quantum Theory (Photonics) Radio Microwaves IR Visible X-ray γ-ray kilo 10 6 Mega 10 9 Giga Tera Peta Exa Zetta Yotta!2

3 Portfolio Systems Mini-Z, Micro-Z, FICO, ZAP, Z3 Components Auto-balanced detector, high-voltage modulators, Photo-conductive antennas, ZAP detector... Research Spectroscopy, Nondestructive evaluation, Imaging, Plasma systems!3

4 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!4

5 Terahertz Technologies Zomega s Core Technology!5

6 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 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!6

7 EO Sampling vs. Photo-Conductive Antennas (detection) Feature Photo-Conductive Antennas EO Sampling Reliability Very sensitive to misalignment; gap size ~10um Less sensitive to misalignment; laser beam and THz overlap ~1 mm more robust Noise Non-differential method; laser noise affects performance Differential method; noise is reduced more effectively higher SNR Bandwidth Typically resonant devices; Bandwidth is limited ~2 THz Non-resonant device; Bandwidth >5 THz!7

8 Terahertz Features 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!8

9 Pulsed Terahertz Operation Modes Non-destructive evaluation Spectroscopy Cracks, voids, and other structural defects Pharmaceutical characterization and drug discovery Thickness and coatings measurement Chemical and biological threat assessment Corrosion inspection Explosive detection!9

10 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!10

11 Examples: Non-destructive Evaluation Foam materials Corrosion under insulation Textile materials Internal structure!11

12 Frequency Dependent Resolution A broadband system contains many frequencies in the pulse Resolution will depend on a particular frequency Higher frequencies show better resolution (shorter wavelength) 300 GHz 1 THz!12

13 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!13

14 Why Terahertz for Thickness Measurements 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!14

15 Thickness Measurement Principle 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!15

16 Plastic Components Front slab measured thickness Nominal thickness mm mm Discrepancy -3% Back slab measured thickness Nominal thickness mm mm Discrepancy -2% Measured inner interface Nominal thickness mm mm Discrepancy 1% 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!16

17 Pharmaceutical Coatings Meas.: 115 um Nom.: 120 um Disc.: 4% Meas.: um Nom.: um Disc.: within interval!17

18 Tera Art Papyrus Mural paintings Pottery 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), 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), 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), Zomega Zomega Terahertz Terahertz Corporation -- PROPRIETARY - DO - NOT DO NOT DISTRIBUTE DISTRIBUTE WITHOUT WITHOUT PERMISSION PERMISSION!18

19 Why Terahertz for Art Inspection 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)!19

20 Finding Goya: Sacrifice to Vesta (1771) X-ray image does not show too much structural information!20

21 Data Acquisition Considerations 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!21

22 Art Inspection 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), doi: /oe !22

23 Fiber-Coupled (FiCO) THz Time-Domain System 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!23

24 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!24

25 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!25

26 Thank You! Questions? Zomega Terahertz Corporation 15 Tech Valley Drive East Greenbush, NY (USA)! Web: Phone: !26