Seek XR (LT-AAA) modding

[Thermalization]

Hey guys,
I have a seek XR that I want to mod, but am unsure of a few things and thought I'd ask them here.

Is the FoV difference between the compact and xr merely due to the lens assembly or is there more to it than that? Would it be possible to make a wide angle lens for the xr?
What trickery gives the xr the claimed 'extra range' over the compact?

I also had some questions about firmware modding and whether it would be possible to do so using nothing but your phone (via a customized or custom made app?)

How do you update the firmware? Through the seek app?

What lenses (ZnSe?) are best suited as replacements for the stock lens?

Is there any way to use the shutter manually? Or any SDK or code examples? Has anyone really modded this thing much? Or do people just not care about modding such a low end thermal?

And lastly, how much must I worry about using this outdoors and sunlight?

-Thomas

[Mechatrommer]

i made purchase of Seek Compact (New Model) after i saw this review...

it seems everything are the same except the lens.

[IwuzBornanerd]

The only difference between the XR & the non-XR is the lens and its mounting apparatus.  The bayonet mount of the non-XR is recessed into the camera lid and the lens holder is smaller in diameter than on the XR.  The lens holder (barrel) on the XR has the same diameter & thread pitch as that of many webcams & "security" cameras, so you could scavenge material from those things to make your own lens mount.  I have done this to make telephoto lenses out of ZnSe laser cutter lenses.  The problem with trying to get a wide angle lens in there is that you would need to find ones that fit inside your lens mount barrel--on the order of 8.5mm diameter--or you won't be able to get it close enough to the sensor to focus.

Another thing relevant to that is that these Seek lenses have a wider field of view than comparable focal length plano-convex lenses.  I have verified that the field of view of the XR in the 206 pixel direction is indeed 20 degrees, and I have accurately measured the distance from the edge of the convex surface of the lens to the top of the sensor as 9.9mm when focused on distant objects.  BUT when I replaced that lens with a plano-convex ZnSe lens of 25mm focal length the field of view shrunk by a factor of 4, not the expected 2.5.  What this means is that if you want to get the field of view of the non-XR with a plano-convex lens you would need about a 3mm focal length and I don't think you could get it that close to the sensor given the way the lid is formed.  You can see images of the lens assemblies on the Seek lens repair thread https://www.eevblog.com/forum/thermal-imaging/seek-thermal-lens-repair/.

The "extra range" is strictly the narrower field of view spreading a smaller area over the sensor area such that smaller objects occupy more pixels and are easier to identify.

I have no knowledge or expertise in the firmware area.

I don't know of anyone who has found a way to control the shutter with software, but you could certainly kluge in some physical means of controlling it.  You would also have to write software to make use of it that way also as you would lose the automatic calibration that is needed to prevent ongoing image degradation.  You can find info. on control commands & available software on GitHub: https://github.com/lod/seek-thermal-documentation/wiki/Seek-Software

I have had a couple of these running outside in sub-freezing temperatures as well as in the 80s Fahrenheit with no real trouble, except some strange phenomena show up as they get below the 60sF.  They are not at all sealed aginst the elements so you don't want to leave them out in the rain.  I have not tried pointing one at the sun but I don't recommend it.  There has been discussion about that elsewhere on this board, though.

[Thermalization]

The only difference between the XR & the non-XR is the lens and its mounting apparatus.  The bayonet mount of the non-XR is recessed into the camera lid and the lens holder is smaller in diameter than on the XR.  The lens holder (barrel) on the XR has the same diameter & thread pitch as that of many webcams & "security" cameras, so you could scavenge material from those things to make your own lens mount.  I have done this to make telephoto lenses out of ZnSe laser cutter lenses.  The problem with trying to get a wide angle lens in there is that you would need to find ones that fit inside your lens mount barrel--on the order of 8.5mm diameter--or you won't be able to get it close enough to the sensor to focus.

Another thing relevant to that is that these Seek lenses have a wider field of view than comparable focal length plano-convex lenses.  I have verified that the field of view of the XR in the 206 pixel direction is indeed 20 degrees, and I have accurately measured the distance from the edge of the convex surface of the lens to the top of the sensor as 9.9mm when focused on distant objects.  BUT when I replaced that lens with a plano-convex ZnSe lens of 25mm focal length the field of view shrunk by a factor of 4, not the expected 2.5.  What this means is that if you want to get the field of view of the non-XR with a plano-convex lens you would need about a 3mm focal length and I don't think you could get it that close to the sensor given the way the lid is formed.  You can see images of the lens assemblies on the Seek lens repair thread https://www.eevblog.com/forum/thermal-imaging/seek-thermal-lens-repair/.

The "extra range" is strictly the narrower field of view spreading a smaller area over the sensor area such that smaller objects occupy more pixels and are easier to identify.

I have no knowledge or expertise in the firmware area.

I don't know of anyone who has found a way to control the shutter with software, but you could certainly kluge in some physical means of controlling it.  You would also have to write software to make use of it that way also as you would lose the automatic calibration that is needed to prevent ongoing image degradation.  You can find info. on control commands & available software on GitHub: https://github.com/lod/seek-thermal-documentation/wiki/Seek-Software

I have had a couple of these running outside in sub-freezing temperatures as well as in the 80s Fahrenheit with no real trouble, except some strange phenomena show up as they get below the 60sF.  They are not at all sealed aginst the elements so you don't want to leave them out in the rain.  I have not tried pointing one at the sun but I don't recommend it.  There has been discussion about that elsewhere on this board, though.

Fantastic reply, thank you. Would you say the xr is preferable (macro lens of course) for pcb work? Or would the compact's wider field of view be preferred?

[Bill W]

Another thing relevant to that is that these Seek lenses have a wider field of view than comparable focal length plano-convex lenses.  I have verified that the field of view of the XR in the 206 pixel direction is indeed 20 degrees, and I have accurately measured the distance from the edge of the convex surface of the lens to the top of the sensor as 9.9mm when focused on distant objects.  BUT when I replaced that lens with a plano-convex ZnSe lens of 25mm focal length the field of view shrunk by a factor of 4, not the expected 2.5. 

What this actually means is that the 'simple lens equivalent' of the Seek lens is not in the same place as the front/only element. 
The focal length rules trump mechanics and the real focal length is about the 7mm expected - 20 degrees field of view, 12um sensor, 206 pixels.

regards
Bill

[IwuzBornanerd]

Does this mean that the term "focal length" does not necessarily refer to a physically measurable distance between a focal plane and some point within the physical body of a lens? 

The reason I referred to the convex surface of the lens is because it is the one closest to the sensor; the surface we see from outside the camera is concave.  I realize that the "thin lens" approximation is just that and not always applicable (and I don't think it applies to the Seek lenses), but I have not been able to find anything that has enabled me to understand how the Seek lens could be considered a 7mm focal length when it is impossible for any molecule of that lens to be any closer to the sensor than 9mm (maybe 8 with the focus restriction removed) given where it is mounted in the camera and the adjustment range of the mount.

Edit:
No, wait, I think I've got it.  It finally dawned on me a couple hours before sunrise today...The focal length Bill W is talking about is the "effective focal length" or perhaps more correctly the "simple-convex-lens-equivalent" focal length; that is, the focal length of a thin single or double convex lens having the same field of view as that of the actual Seek lens, or the same magnification relative to a "standard" convex lens.  This is the standard convention used with zoom lenses on SLR cameras and I'm okay with that and never give it a thought, but it bothers me here, probably only because I am thinking about it and was trying to directly measure the physical focal length of the Seek lens.  What makes this case strange is that the actual lens is farther from the sensor than the simple convex equivalent whereas with most telephoto zoom lenses the lens [group] is closer to the sensor than the simple convex equivalent lens.  The "effective focal length" is more useful than the actual focal length of the lens because, as with SLR cameras, it enables one to use consistent F-stop and shutter speed values regardless of the complexity of the lens.  So when someone asks what the focal length of the Seek XR lens is, what they "want" to hear is 7mm so they can then see that it has an f/1.4 aperture which they can compare with other thermal cameras.

It has been my intent to bring this subject up back on the lens repair thread AFTER I collected some more data and did some simulations with lens ray tracing software, but I have not met my prerequisites on that yet.  I have been suspecting that the formula which yields that 7mm from the field of view & sensor pitch was only valid for the thin lens approximation, but, again, I have not found anything that deals with that for different lens configurations...And with the above realization, maybe I don't need to bring it up any more. 

[IwuzBornanerd]

Fantastic reply, thank you. Would you say the xr is preferable (macro lens of course) for pcb work? Or would the compact's wider field of view be preferred?

I was hoping someone who uses the camera for pcb work would address this since I have not done much of that, but if you need to distinguish tiny parts you will primarily need close focus, and from what I have read on this board it seems that close focus it the big desire.  The non-XR will focus closer but the wider field of view at least partly offsets that advantage.  You can use the field of view to calculate the smallest feature you will be able to detect at a given distance.  For a 0102 resistor to occupy 2 pixels I get a distance of 5.8 inches with the 20 degree FOV.  You would have to remove the focus restriction or use an added lens to focus that close with the XR.  I get 3.17 inches with the 36 degree FOV.  I think someone on here said he could focus the non-XR that close without removing the focus restriction. but I can't verify that since I have removed that restriction from mine. 

[Bill W]

No, wait, I think I've got it.  It finally dawned on me a couple hours before sunrise today...The focal length Bill W is talking about is the "effective focal length" or perhaps more correctly the "simple-convex-lens-equivalent" focal length; that is, the focal length of a thin single or double convex lens having the same field of view as that of the actual Seek lens, or the same magnification relative to a "standard" convex lens.  )

Yes that is it, although it is a very real focal length, and obeys all the rules of optics for field of view and aperture.  An example is a lens I have here, it is 8.6mm focal length but is 14mm through the optics and the rear element sits more than 9mm in front of the sensor image plane for infinity focus. 
It's idealised thin lens equivalent is behind the whole assembly.
The need for a shutter / cal flag does nasty things to lenses in thermal cameras.

regards
Bill