Flir One closeup lens

[nyarvin]

In one of his thermal imaging teardown videos, Mike Harrison shows a lens being held in front of a thermal imager to get a closeup view.  I wanted that capability for my Flir One, except I didn't want to hold the lens by hand; the attached images show what I came up with.  The lens holder is machined (using a lathe) from a 1-inch polypropylene rod; it's a press fit both to the lens and to the circular area on the Flir One that has both of the cameras in it.  The lens is from ebay, and is of course a thermal IR lens -- this one is germanium, but zinc selenide will also do.  The polypropylene completely obscures the visible-light lens, in effect turning off that functionality (the image ends up completely blurred, so no edges are present to display), which is what I wanted anyway since parallax would be a pain to get adjusted right.

Anyway, it works fine.  Or, well, this first lens, with a focal length of 15mm, seemed a bit too powerful; I did another with a ZnSe lens with a focal length of 3 inches which seems about right for looking at PCBs.  (Since the Flir One is normally focused somewhere near infinity, the lens's focal length is about the distance at which things are in focus when the lens is used on top of the Flir One.)

Perhaps the way to do this for a wider audience would be via 3D printing, with more positive retention both of the lens in the holder and the holder to the Flir One; I'm thinking of arms that go around the Flir One and clip on.  The retention on this one is better than I'd expected, and for my own purposes it doesn't seem worthwhile to try to improve it, but if designing it for more people it'd be worth improving.  One would need a pretty accurate 3D printer, though.

[maxbot]

Very well done !

I am looking for a way to attach those lenses to the DIY-Thermocam, which also uses a FLIR Lepton3 as sensor.

Do you have a link to those two lenses you tried ? Not sure how I will do the construction so far, because the case is different to the FLIR One.

How thick are those lenses ? If possible, I will make a press-fit 2d laser cut construction with one or several layers, because the enclosure is also made like this. It could then be attached to the front of the lepton lense crop by two or three screws.

[Fraser]

The seller of those 15mm FL Germanium lenses is a member of this forum.  He is selling them for great price on eBay.com. Just search for Germanium lens and find the one with 15mm FL. He very kindly sent me some for experimentation. They are a quality Thorlabs product. The FL is too short for general use though. An FL of 50mm to 60mm seems to be preferred by most users. I use 50mm, 63mm and 100mm ZnSe lenses for PCB work. Several useful diameters are available cheaply, thanks to them being used in CO2 laser cutters. Just search for ZnSe on eBay and you will find many Chinese suppliers.

Nice work on the lens holder. A 3D printer version would be great if someone has the time to create the file.

Note that the MSX is a PITA when it comes to close up work or low light use. The VL camera AGC ramps up and noise is injected into the image. 3rd party software from a fellow forum member enables you to switch off the MSX and gain the full 160 X 120 pixel resolution.

The program is detailed and available for free in this area of the forum

Fraser

[maxbot]

Thanks for the explanation 

Would this one be okay for PCB work: http://www.ebay.de/itm/New-ZnSe-Focal-Lens-for-CO2-Laser-Cutting-Engraving-Diam-12mm-FL-50-8mm-/252383341620?hash=item3ac3382c34:g:KdMAAOSw8vZXL~4K

Does it have to be mounted directly above the lepton shutter or is a distance of 3-4mm also okay ? I ask because the backplate of my enclosure has a height of 3mm, and I would like to add it as an optional part behind it. Otherwise, I would need to make a special backplate, that can be switched and already has the lense integrated.

[nyarvin]

I measure the ZnSe lens I used at about 2.10 mm thick.  (Oddly, this seems to be about the same in the middle as at the edges; I'm not quite sure how the lens can work.  Looking at the reflections, there's definitely a curved surface in there somewhere, and it does magnify in visible light as well as thermal.)  The germanium lens is about 2.58mm thick in the center and 2.24mm thick on the edges.

Standing the lens off by a distance of 3-4mm would be fine, at least with the ZnSe lens; that's about how much mine is standing off from the surface of the thermal window on the Flir One.

But if starting with the bare Lepton module, you might find it easier on the whole to make the existing lens focusable; that's certainly a better solution, since there are fewer lens surfaces that will get dirty and need cleaning, and since that way the focus can be varied continuously.  Well, provided that there's a good way to reset the focus to default -- clear markings on the focusing ring, or a detent or something.

[trevwhite]

In one of his thermal imaging teardown videos, Mike Harrison shows a lens being held in front of a thermal imager to get a closeup view.  I wanted that capability for my Flir One, except I didn't want to hold the lens by hand; the attached images show what I came up with.  The lens holder is machined (using a lathe) from a 1-inch polypropylene rod; it's a press fit both to the lens and to the circular area on the Flir One that has both of the cameras in it.  The lens is from ebay, and is of course a thermal IR lens -- this one is germanium, but zinc selenide will also do.  The polypropylene completely obscures the visible-light lens, in effect turning off that functionality (the image ends up completely blurred, so no edges are present to display), which is what I wanted anyway since parallax would be a pain to get adjusted right.

Anyway, it works fine.  Or, well, this first lens, with a focal length of 15mm, seemed a bit too powerful; I did another with a ZnSe lens with a focal length of 3 inches which seems about right for looking at PCBs.  (Since the Flir One is normally focused somewhere near infinity, the lens's focal length is about the distance at which things are in focus when the lens is used on top of the Flir One.)

Perhaps the way to do this for a wider audience would be via 3D printing, with more positive retention both of the lens in the holder and the holder to the Flir One; I'm thinking of arms that go around the Flir One and clip on.  The retention on this one is better than I'd expected, and for my own purposes it doesn't seem worthwhile to try to improve it, but if designing it for more people it'd be worth improving.  One would need a pretty accurate 3D printer, though.

Hi Nyarvin, do you have any pictures taken using the lens? I just bought a Flir ONE and will buy a lens but it looks like from Ebay it is going to take at least 3 weeks to get here. Be nice to see some images to show how well the lens does.

Trev

[nyarvin]

No pictures handy, but I recommend just using the unit as is first and seeing if it'll do.  With its small sensor and small lens, focus isn't that critical; this is a "nice to have" sort of addon, not an "essential" one.

[trevwhite]

Thanks for the message. It seems okay really as is but I ordered a lens to experiment with. Out of the box the focal length is 15cm I believe. I have gone for a 50mm focal length lens just to see how it focuses.

[Uho]

For the module, I did this mount. I attached the 3d model.

[Uho]

Mount for Flir One 2 generation. If anyone needs a 3d model I can lay out.

[Uho]

I shot a video about the macro lens holder for Flir One. You can see the 3D printer control board. Germanium lens. Focal length 35 mm.
https://youtu.be/WmetAMWYCt8