Saturday, October 06, 2018

Polarization Sensing in LWIR Band

KB ViTA kindly sent me an info about their latest LWIR camera that senses polarization:

"It all was started with the fact KB ViTA has developed a very sensitive thermal imaging module VLM640, which had a sensitivity of at least 20 mK in 8 — 12 ┬Ám band. The sensor manufacturer turned to KB ViTA and offered an engineering sample from an experimental wafer of bolometric detectors with integrated polarization filters. For KB ViTA it was honorable but, at the same time, there was no understanding of what it is expected to ultimately obtain. The technology and the very idea of seeing the own polarization of the thermal photons of objects that surround us is absolutely new and hardly anyone has experience of processing such information.

Below we will show you how the polarization in the IR spectrum looks.

There were a polarizing sensor and electronics from VLM640 camera with 20 mK sensitivity. The interesting thing about the sensor is each pixel in the group of four is covered with a polarizer. The polarization of each filter differs by 45deg. As a result, the polarization angles are 0—180deg, 45—225deg, 90—270deg, 135—315deg.

In the resulting videos, there are three images (from left to right): video from a conventional thermal imager, reconstructed polarization angles, a complex image, where the brightness is thermal radiation and the color is the polarization angle.

The example videos below show a light bulb and a painted box:

"So far, KB ViTA can say polarization shows us the object surface quality.
There are assumptions (based on the results of communication with the detector manufacturer, colleagues at exhibitions and very scarce information on the Web) that the effect of evaluating the polarization of radiating and reflecting objects can be used in the following areas:

  1. The difference between objects own radiation and reflection (for example, a warm car and a glare of the sun in a puddle or sand).
  2. Search for camouflaged objects.
  3. Oil stains detection on the water surface. 
  4. Defect search.
  5. 3D scanning.
  6. Detection of warm objects on a water surface (a drowning person, for instance), distinguishing its own radiation from reflected light on water."

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