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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.

Anuj Patil
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3 Answers3

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I just measured spectral response of a raspberry pi NoIR camera module using 2inch integrating sphere and monochromator. The first spectrum I did just using NoIR camera module, the second one with a blue filter which I got together with the camera. Also, I did transmittance spectra of the filter for reference. I would like to apologize for the low spectral resolution and that the data is not normalized as I didn't have enough time. If someone is interested, I can repeat the test using a higher resolution.

NoIR module spectral response NoIR module spectral response with the blue filter Transmittance spectra of the blue filter

[Update] Finally, I have time to run the spectrum in a range 350nm - 1200nm. I did the test as the last time. Pi NoIR camera connected to PI Zero was attached to a Thorlabs integrating sphere which was placed inside a fluorescent spectrometer where I can generate a specific wavelength.

Horibo Duetta fluorescent spectrometer was used as a light source. Bandwidth 2nm/ slit enter link description here Thorlabs integrating sphere enter link description here

enter image description here

Here is the raw data split into 3 channels.

enter image description here

Here is the spectral response from a blank sample for your reference. enter image description here

Here is the link to raw images: enter link description here

Here is the link to a script I used to convert images to a spectrum: enter link description here

Anton
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    I am definitely interested in seeing higher resolution versions! Is one interested person enough? – adr Jul 30 '20 at 16:09
  • Two interested people now :) – Ruslan Aug 30 '20 at 18:47
  • Hi guys, sorry for haven’t reply for a long time. I forgot to switch on notifications. I’m a bit busy right now. Let me see what can I do – Anton Mar 05 '22 at 07:33
  • @Anton could you provide the data used to generate these curves? Thank you! – deox Mar 17 '22 at 16:39
  • @deox Please find the updated data. Let me know if you have more questions. Hope it helps. – Anton Jul 08 '22 at 03:55
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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

Moged
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  • Nice! Simple answer based on fundamental physics. – not2qubit May 09 '18 at 19:37
  • @moged how then do we have instruments which capture infra red wavelengths? Something other than a CCD? – carl crott Oct 06 '18 at 17:22
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    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 07 '18 at 22:10
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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

not2qubit
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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 08 '18 at 09:10
  • Yes! You're right. I totally missed that word! What a waste of research effort, not to use the *NoIR* camera module. – not2qubit May 08 '18 at 12:58
  • Still very unlikely you will have any response at that wavelength. See my update. – not2qubit May 08 '18 at 13:26