Imaging beyond the visible - An Overview of Short-Wave Infrared (SWIR) Technology for Machine Vision

Imaging beyond the visible An Overview of Short-Wave Infrared (SWIR) Technology for Machine Vision

Paul Maria Zalewski, Business Development Manager5th November 2014, Stuttgart

Contents

Short-wave Infrared Technology

Differences between SWIR and CCD/CMOS cameras

Industrial Applications & Benefits of Short-wave Infrared- Semiconductor- Photovoltaics- Glass Industry- Plastic Sorting with Hyperspectral Imaging

Conclusion

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What is Short-wave Infrared?

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SWIR900-2500nm

Visible400-750nm

NIR750-1000nm

2,500400 750 1,700900 1,000Wavelength [nm]

CCD/CMOS

NIR Enhanced CCD/CMOS

Standard InGaAs

2,200

Extended InGaAs

Imaging beyond the visible | 05/11/2014 |

What differs a SWIR camera from a classic Machine Vision camera?

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Cooling CapabilityDue to the higher Dark Current of InGaAs sensors, cooling is necessary

InGaAs DetectorSensitivity between 900 and 1,700 nmHigh complexity level in the production processDefect pixels on every sensorNon-uniform pixel behavior Higher dark current than CCD, CMOS

More IntelligenceAdvanced image correction featuresNon-uniformity correction (NUC)Defect Pixel CorrectionBackground Correction

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2

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Basic Structure of a SWIR Camera

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InGaAsSensor

Optics&

Filters

Sensor Cooling

Intelligence &

Electronics

Interface&

I/O Control


Effect on the Image Quality with Cooling and more Intelligence

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Sensor Temp. +40°C 100ms Exposure Time1

Apply Cooling Sensor Temp. -5°C2

Increase Exposure Time 800ms3

Apply IntelligenceNon-Uniformity Correction (NUC)4

Apply more IntelligenceDefect Pixel Correction5


A Selection of SWIR Applications

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Industrial Machine Vision

Semiconductor Photovoltaics Chemical (gas, plastic, foil) Pharmaceutical Glass Production Agriculture Food

Scientific & Medical

Optical Coherence Tomography Microscopy Hyperspectral Imaging Laserbeam Profiling Airborne Remote Sensing Art Inspection

Security & Traffic

Surveillance Vision Enhancement Night Vision Homeland Security


Semiconductor Industry

Applications

Silicon Crystal & Ingot Inspection

Wafer Inspection

Wafer Level Packaging

3D-IC Defect Inspection with Infrared Microscopy

Photon Emission Microscopy

Photovoltaics


What makes SWIR so special for Semiconductor Inspection?

Silicon gets transparent at wavelengths above 1,100 nm

SWIR has a great sensitivity at 1,000 nmInGaAs CameraQE of ≈ 76% at 1,000 nm

CCD/CMOS NIR Enhanced CameraQE of ≈ 3% at 1,000 nm

The higher the thickness of the wafer (≈ >20µm), the more reasonable is an InGaAs camera

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76%

3%


Luminescence imaging helps to identify non-uniformities in the silicon wafer or solar cell by forcing it to emit light:

Electroluminescence (EL)

Photoluminescence (PL)

Some emission effects to characterize photovoltaics intermediates are only visible in SWIR …

… or partially with CCD/CMOS, but with extreme long exposure times (Seconds instead of Milliseconds)Thinfilm based solar cells show other effects

- e.g. Copper Indium Diselenide (CIS) at a wavelength of 1,330 nm

What makes SWIR so special for Photovoltaics Inspection?


Glass Production

Hot-End Glass InspectionMonitoring of glass temperatureuniformities and cooling rate

Interior and exterior inspection

Improvement of yield and quality


What makes SWIR so special for Hot-End Glass Inspection?

Typical: Temperature Measurement between 250°C to 800°C

Based on the Planck’s radiation lawExtended Temperature Measurements possibleSWIR cameras can image through glass

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Reference temps:White hot steel ~1200 °CMelting point of aluminum 660 °CWater boils at 100 °CUncooled camera at 38 °CHuman body at 37 °C, radiates at ~ 10 μmWater freezes at 0 °C


Hyperspectral Imaging (HSI)

HSI combines digital imaging with spectroscopy to obtain detailed information across multiple ranges of the electromagnetic spectrum

Applications:Recycling & Plastic Sorting

Geology & Mineral Inspection

Pharmaceutical Quality Control

Food & Agriculture

Medical e.g. Disease Diagnosis


What makes SWIR so special for Hyperspectral Imaging?

Each inorganic material has a differentchemical composition and crystallinestructure resulting in an unique spectralresponse corresponding to its specificlight absorption characteristics

Illustration shows the unique information content of five different sorts of plastic starting with 1,000 nm

In general, the higher the wavelength in the application, the higher the spectral information content

- 400 nm to 1,000 nm (basic information)

- 900 nm to 2,500 nm (extended or unique information)

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Source: Middleton Research


Conclusion

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There are basically three technical differences between SWIR and CCD/CMOS cameras

Photon detector material (InGaAs vs. Si)

Cooling capabilities needed to reduce noise

More Intelligence: Advanced image correction features

Take SWIR into consideration and explore your application with new eyes!

SWIR cameras offer new physical effects in the Short-wave Infrared spectrum

SWIR helps you to improve the yield in terms of quality, as well as productivityDetect defects more accurately and much faster

Extraordinary reduction of exposure times


Thank you very much!

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Paul Maria ZalewskiBusiness Development Manager– Infrared & Scientific –

[email protected]

Allied Visionwww.alliedvision.com


http://www.alliedvisiontec.com/

http://www.alliedvision.com/

Imaging beyond the visible - An Overview of Short-Wave Infrared (SWIR) Technology for Machine Vision

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