From Algorithm development to Industrial product


Light is an electromagnetic wave, with

  • Amplitude perceived as brightness
  • Wavelength perceived as color
  • But the orientation of the
    wave oscillation is not visible

Properties of Polarization:

  • All orientations equally present
    --> degree of polarization 0%
  • Only one strong orientation
    --> degree of polarization 100%
  • All orientations are present
    but at different strength
    --> partially polarized, e.g. 50%
  • Dominant angle of polarization
    --> another degree of freedom

Where does it come from?

Most light sources (except lasers) are unpolarized

  • Reflection gives polarized light, think of water surfaces, glass, beamsplitters surface inspection, ellipsometry
  • Reflection at non-metallic surfaces like human skin, plants, plastics, object classification
  • Nanostructures can create polarization in transmission and reflection, useful for polarization filters, carbon fiber inspection

Application to Carbon Fiber Reinforced Plastics (CFRP) Inspection

Without polarization

With polarization

Application to Stress Inspection in Glass


Measuring Polarization

  • Polarization has 3/4 degrees of freedom
    • Intensity of light
    • Degree of polarization
    • Angle of maximum polarization
    • (Circularity)

We can use ≥3 measurement with polarization filters for analysis
(and some math to obtain Stokes parameters)

But from there: 

  • How to process the raw sensor data?
    • Different from RGB debayering
    • How do you calibrate measurements?
    • Achieving reliable data for measurements
  • How to solve the applications
    • What is a good setup?
    • The user does not need polarization values
    • More processing is required to calssify
      industrial products for quality (good/bad)


Algorithm development with internal prototype camera

  • Image processing for evaluating
    different modes/calculations
  • Extending SciLab
    • Interfacing an industrial USB
      camera for live image capture
    • Interfacing a step motor controller
      for defined filter rotation

 Processing Stack for Prototype System



Product Development: For integration into industrial inspection systems

  • Use upcoming industrial cameras
    • 5 MPixel, single-shot imaging
    • High frame rate for inline inspection
  • Provide the software as extension/plugin/.dll
    for machine vision software
  • Calibrated measurements of retardation/ATN
  • Measurement of magnitude and orientation of stress

From Scilab Code to a .dll

  • Re-programm everything again
  • Transfer into parallel C code
  • Utilize parallel architectures
  • Take into account:
    • Worst-case execution time
    • hard realtime applications

 Toolflow used

 Processing Stack for Commercial Solution