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I wish to create a pattern using 1500nm laser and analyse the images.Will any Pi-Cam (NOIR) capture this?

Link to research regarding camera characteristics with respect to wavelength upto 1500nm would be very helpful.

  • do you have the laser and the Pi-Cam? – jsotola May 7 '18 at 7:09
  • I'd assume the NOIR camera would – Jaromanda X May 7 '18 at 8:33
  • Which PiCam do you have? – not2qubit May 7 '18 at 9:06
  • No, I don't have one right now. Off course I'd prefer NOIR but I couldn't find any application/research done with 1500nm light/laser. – Anuj Patil May 8 '18 at 9:06
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Neither one of the available PiCam's can see the part of the spectrum you are looking for. Unfortunately the data sheets for either one are incomplete and doesn't show a valid frequency response of either,

  • The V1 is using the Omnivision 5647 (no spectral info available)
  • The V2 is using the Sony IMX219 sensor with a light response up to 700 nm. (NIR)
  • The V2.1 "NoIR" is also using the Sony IMX219 sensor, but without an IR filter; "No IR" with (AFAIK) unknown IR response.

Fortunately someone has written up a research paper on the V2 camera.

The IMX219 sensor operates in the visible spectral range (400 to 700 nm) and uses a Bayer array with a BGGR pattern.


EDIT

Apparently the research was performed on the normal (non-NoIR) camera module, that has the IR filter.

"The Raspberry Pi also provides a visible and near-infrared version of the Sony IMX219 called the NoIR camera. This camera has No infrared (NoIR) filter on the lens, which allows imaging beyond the visible range. In this paper, the NoIR version was not considered."

This invalidates the spectral response stated below.

However, it is still extremely unlikely to cover the FIR region up to 1500 nm, since that region is difficult even for professional devices like the FLIR One:

The Lepton sensor detects infrared in the "long wavelength" region, between 8 and 14 μm.


This is the spectral response they found for the normal module:

enter image description here

Compare this to the response in the Datasheet:


enter image description here

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    Thanks for the reply! Apparently the research has been done with IR cut filter on the sensor. To analyze frequency response beyond visible, the same experiment needs to be carried out without the filter and upto 1500nm wavelength. – Anuj Patil May 8 '18 at 9:10
  • Yes! You're right. I totally missed that word! What a waste of research effort, not to use the NoIR camera module. – not2qubit May 8 '18 at 12:58
  • Still very unlikely you will have any response at that wavelength. See my update. – not2qubit May 8 '18 at 13:26
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The silicon bandgap is about 1 eV. That means a photon with wavelengths more than ~1000 nm do not have the energy to generate a charge. https://www.spiedigitallibrary.org/conference-proceedings-of-spie/5677/0000/Infrared-response-of-charge-coupled-devices/10.1117/12.610650.full

  • Nice! Simple answer based on fundamental physics. – not2qubit May 9 '18 at 19:37
  • @moged how then do we have instruments which capture infra red wavelengths? Something other than a CCD? – carl crott Oct 6 '18 at 17:22
  • Silicon has a bandgap of ~1 eV and hence a wavelength cutoff of ~1000nm. Gallium arsenide and germanium are materials that can be used for longer wavelengths. One can buy sensors, made of these materials, that cover for instance the 1550 nm that precipitated this post. – Moged Oct 7 '18 at 22:10

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