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Really really cool! Will have to give this a try with my monochrome camera. I wish there was a bit more detail on possible lenses, its hard to find optics that

Really really cool! Will have to give this a try with my monochrome camera. I wish there was a bit more detail on possible lenses, its hard to find optics that work well past 1000nm. It’s pretty interesting how much the fall off is between 920 to 1070nm - on my camera, 920nm can be exposed perfectly in daylight at around 1/10th of a second, 1070nm needs 4 minutes worth of time to match the same exposure!

deleted 4y ago
[deleted]
bunnie 4y ago
Hi! thanks, I'm the post's author. I had the same concern you have about finding "just the right lens", but was pleasantly surprised to find the $180 camera/lens combo linked in the post worked just fine. In fact basically every piece of optics I had in my lab could pass light at 1050nm, and I have a bit of everything from cheap stuff bought over the counter in Shenzhen to brand-name microscopes. I tried lenses from 6 different vendors and they all worked about the same in terms of passing light (but of course the fidelity of the image scales with cost, better lens tolerances are just more expensive). My guess is that uncoated glass should be transparent in the 1050nm band, but some lenses have AR coatings that limit the bandwidth. A lot of my lenses do have AR coating (based on the greenish tint I see in the reflections), but I guess the bandwidth of the coating used on most visible-light lenses is just wide enough for 1050nm to slide through.
- buildbot 4y ago
  That's very good to know, thanks for the response! Love your work :)
formerly_proven 4y ago
Looking around, normal industrial (like Pregius) or CCTV (Starvis) sensors are only optimized up into the ~950nm range and drop to near-zero rapidly. The NIR-optimized Starvis seem to be a lot better than normal general purpose sensors already (not sure if this difference comes mainly from different Bayer arrays, in the QE curves these have a very, very distinct hump in the 850-950nm where R/G/B channels seem to have a bandpass). There are some sCMOS cameras (like PCO's stuff [1]) which would seem to be about an order of magnitude more sensitive at 1050 nm than these. And then there's of course the famed "black silicon". [2] My money would be on InGaAs sensors [3] being the best in this range. I would also suspect these are subject to funny import/export restrictions, nevermind the price. [1] https://www.pco.de/scientific-cameras/pcopanda-42-bi/ https://www.pco.de/scientific-cameras/pcopanda-42-bi/ ~10% QE at 1050 nm [2] https://1.bp.blogspot.com/-wrj9PudX2YM/WkSB-PL-9vI/AAAAAAAAQUY/8QH-MqHYLVIMZig4zfmUNbfFsOBS13h-ACLcBGAs/s640/82a02ffc7bc8272a7dde8e39aa5486.jpg https://1.bp.blogspot.com/-wrj9PudX2YM/WkSB-PL-9vI/AAAAAAAAQ... [3] https://www.princetoninstruments.com/wp-content/uploads/2020/08/B-CCD-vs-InGaAs-QE-1024x681.png https://www.princetoninstruments.com/wp-content/uploads/2020...
- buildbot 4y ago
  I do wonder what silicon difference a NIR optimized starvis would have vs. the consumer IMX211 silicon, smaller monochrome sensors of the same gen seem fine past 1000NM. Bayer filters would make sense as the actual difference.
alexbock 4y ago
I enjoy monochrome infrared photography at wavelengths longer than 1000 nm using a Sigma sd Quattro (no Bayer filter and the sensor IR filter is reversibly user-removable). To reduce exposure times as much as possible, I've been testing an AR-coated near infrared achromatic doublet (AC254-050-B-ML) with a 3D-printed housing to attach it to the camera mount with a manual focusing barrel. The next step is to design a fast double gauss lens that can similarly be assembled from readily available NIR-coated stock lens elements.
- buildbot 4y ago
  I've wondered about doing this a lot! How is the image quality with the doublet? I love the Quattro series of cameras but hate the software personally. I may someday pick up a sd Quattro H...
  - alexbock 4y ago
    The center of the image it produces is perfectly sharp, but using a single achromatic doublet as a photographic lens at f/2 necessarily produces significant eighteenth-century softness as you move out to the edges. This image [1] taken to demonstrate that red wine (left) is clear and nearly as transparent as water (right) in the near infrared provides a decent example of how the images it produces wide open soften outside the center much more quickly than modern commercial camera lenses which typically don't lose sharpness at maximum aperture until the corners. However, the sd Quattro is sensitive enough from 1000 nm - 1100 nm that I can take handheld shots outdoors on a sunny day while stopped down to f/5.6, and the smaller aperture gives more consistent sharpness across the frame. It also only takes a few seconds exposure on tripod to capture astrophotography of red giant stars that emit significant infrared like Betelgeuse. Incidentally, the original reason I wanted an infrared-sensitive camera and a 1000 nm long pass filter was to photograph stars in the sky during the middle of the day, taking advantage of the quartic dependence on wavelength in Rayleigh scattering to remove the overpowering brightness of the sky. [1] https://alexbock.github.io/blog/nir-examples/near-infrared-850nm-redwine-vs-water.jpg https://alexbock.github.io/blog/nir-examples/near-infrared-8... (note: this image used an 850 nm long pass filter rather than 1000 nm but was taken with the same doublet described before)

deleted 4y ago

[deleted]

bunnie 4y ago

Hi! thanks, I'm the post's author. I had the same concern you have about finding "just the right lens", but was pleasantly surprised to find the $180 camera/lens combo linked in the post worked just fine. In fact basically every piece of optics I had in my lab could pass light at 1050nm, and I have a bit of everything from cheap stuff bought over the counter in Shenzhen to brand-name microscopes. I tried lenses from 6 different vendors and they all worked about the same in terms of passing light (but of course the fidelity of the image scales with cost, better lens tolerances are just more expensive). My guess is that uncoated glass should be transparent in the 1050nm band, but some lenses have AR coatings that limit the bandwidth. A lot of my lenses do have AR coating (based on the greenish tint I see in the reflections), but I guess the bandwidth of the coating used on most visible-light lenses is just wide enough for 1050nm to slide through.

buildbot 4y ago
That's very good to know, thanks for the response! Love your work :)

formerly_proven 4y ago

Looking around, normal industrial (like Pregius) or CCTV (Starvis) sensors are only optimized up into the ~950nm range and drop to near-zero rapidly. The NIR-optimized Starvis seem to be a lot better than normal general purpose sensors already (not sure if this difference comes mainly from different Bayer arrays, in the QE curves these have a very, very distinct hump in the 850-950nm where R/G/B channels seem to have a bandpass). There are some sCMOS cameras (like PCO's stuff [1]) which would seem to be about an order of magnitude more sensitive at 1050 nm than these. And then there's of course the famed "black silicon". [2] My money would be on InGaAs sensors [3] being the best in this range. I would also suspect these are subject to funny import/export restrictions, nevermind the price. [1] https://www.pco.de/scientific-cameras/pcopanda-42-bi/ https://www.pco.de/scientific-cameras/pcopanda-42-bi/ ~10% QE at 1050 nm [2] https://1.bp.blogspot.com/-wrj9PudX2YM/WkSB-PL-9vI/AAAAAAAAQUY/8QH-MqHYLVIMZig4zfmUNbfFsOBS13h-ACLcBGAs/s640/82a02ffc7bc8272a7dde8e39aa5486.jpg https://1.bp.blogspot.com/-wrj9PudX2YM/WkSB-PL-9vI/AAAAAAAAQ... [3] https://www.princetoninstruments.com/wp-content/uploads/2020/08/B-CCD-vs-InGaAs-QE-1024x681.png https://www.princetoninstruments.com/wp-content/uploads/2020...

buildbot 4y ago
I do wonder what silicon difference a NIR optimized starvis would have vs. the consumer IMX211 silicon, smaller monochrome sensors of the same gen seem fine past 1000NM. Bayer filters would make sense as the actual difference.

alexbock 4y ago

I enjoy monochrome infrared photography at wavelengths longer than 1000 nm using a Sigma sd Quattro (no Bayer filter and the sensor IR filter is reversibly user-removable). To reduce exposure times as much as possible, I've been testing an AR-coated near infrared achromatic doublet (AC254-050-B-ML) with a 3D-printed housing to attach it to the camera mount with a manual focusing barrel. The next step is to design a fast double gauss lens that can similarly be assembled from readily available NIR-coated stock lens elements.

buildbot 4y ago
I've wondered about doing this a lot! How is the image quality with the doublet? I love the Quattro series of cameras but hate the software personally. I may someday pick up a sd Quattro H...
- alexbock 4y ago
  The center of the image it produces is perfectly sharp, but using a single achromatic doublet as a photographic lens at f/2 necessarily produces significant eighteenth-century softness as you move out to the edges. This image [1] taken to demonstrate that red wine (left) is clear and nearly as transparent as water (right) in the near infrared provides a decent example of how the images it produces wide open soften outside the center much more quickly than modern commercial camera lenses which typically don't lose sharpness at maximum aperture until the corners. However, the sd Quattro is sensitive enough from 1000 nm - 1100 nm that I can take handheld shots outdoors on a sunny day while stopped down to f/5.6, and the smaller aperture gives more consistent sharpness across the frame. It also only takes a few seconds exposure on tripod to capture astrophotography of red giant stars that emit significant infrared like Betelgeuse. Incidentally, the original reason I wanted an infrared-sensitive camera and a 1000 nm long pass filter was to photograph stars in the sky during the middle of the day, taking advantage of the quartic dependence on wavelength in Rayleigh scattering to remove the overpowering brightness of the sky. [1] https://alexbock.github.io/blog/nir-examples/near-infrared-850nm-redwine-vs-water.jpg https://alexbock.github.io/blog/nir-examples/near-infrared-8... (note: this image used an 850 nm long pass filter rather than 1000 nm but was taken with the same doublet described before)