Is 12um pixel size too small ? A topic of discussion - Page 1
Forum section: electronics / general

author: Fraser
author_rank: Super Contributor
timestamp: June 02, 2019, 01:02:33 pm
content: As many will be aware, the Microbolometer FPA built using 12um pixels is now quite common.I have started this thread to discuss the pro’s and con’s of moving to such a small pixel size as I believe potential buyers of the technology should be familiar with the issues surrounding such small pixels.OK we have seen the Lepton and Seek Thermal cameras using the 12um pixel size but, in general, the image produced is noisy and far from that produced by microbolometers that use large pixel sizes such as 35um, 25um and even 17um. We need to ask ourselves whether the issues found with the Lepton and Seek cameras are due to the size of the Microbolometer pixels or other aspects of the camera design, such as the lens and video processing stages.Some basic facts about 12um pixels ........1. Smaller pixels means smaller FPA die sizes for a given resolution and so a greater number of microbolometers per silicon production wafer. This leads to production cost reduction.2. Smaller die sizes enable smaller lens systems to be used and, combined with innovative lens materials, this reduces production costs. Germanium, Chalcogenide IR glass and Silicon lenses are being used. In general, the smaller the diameter of a lens, the lower its manufacturing cost per unit.3. Smaller die sizes enable smaller Microbolometer modules and so facilitates more compact and light weight thermal imaging cores and cameras. The military have a need for miniaturisation of the technology for their infantry drone systems. Smaller thermal core and camera dimensions also increase the marketability of them to OEM’s wishing to integrate such technology into hand held equipment such as test equipment, mobile phones and other compact products. The venerable FLIR TAU 2 would likely not be a mobile phone manufacturers first choice of thermal imaging core for a mobile phone4. Smaller die sizes and miniaturisation of the Microbolometer module have developed in parallel with new manufacturing techniques to reduce production costs, microbolometers are now available with very little metal content and fabrication house friendly structures, including greatly reduced vacuum cavity volume. Some modules use direct bond wires to avoid the need for SMT pads or leads. The simplification of the Microbolometer structure is another contributor to cost reduction to make such technology more appealing to OEM’s and the wider public.5. Improvements in Microbolometer Read Out IC (ROIC) technology has enabled the use of a pixel size that previously proved to have too low a sensitivity. ROIC and image processing performance continues to improve with each generation released and this is a positive aspect of the drive to use smaller and smaller pixel sizes. The advances in the ROIC and video processing may be carried over to the larger pixel size microbolometers to further improve their performance. The 12um pixel is therefore a positive driver in the technology used in thermal imaging cores and cameras.6. Sadly 12um thermal imaging pixels used in the LWIR spectrum are subject to the laws of physics that mean the sensitivity of the pixel to thermal energy reduces as its surface area is reduced in size. A large dimension pixel of say 35um has a surface area that provides excellent thermal sensitivity at the point of scene ‘data’ collection. The signal to noise ratio of the pixel output is excellent for such Microbolometer based technology. There are proven methods of noise reduction, both in the ROIC stage and the video processing that follows. The 12um LWIR pixel is severely disadvantaged in terms of thermal sensitivity. It’s energy collection surface area is significantly reduced, almost to the point of non viability ! The signal to noise ratio that results is poor. With a poor signal to noise ratio at the front end of any system, it will always be a challenge to compete with a system that has a better signal to noise ratio. That is just common sense. As with radio systems, front end signal to noise ratio sets the scene for the whole systems performance. All following stages in the design have to work with that less than ideal signal. They can only use clever software and hardware to compensate for it and, in some cases, hide it from the user of the system. The 12um pixel is a classic example of this scenario. It is without doubt disadvantaged, some would say compromised, by its small pixel size. In order to make the 12um pixel a viable technology for a LWIR camera, the noise contributed by the ROIC combined with the performance of its amplifiers had to be improved. This in combination with advanced video processing designs enabled the 12um pixel based Microbolometer to perform to an acceptable level for the intended tasking. We then saw the release of the FLIR Lepton that provided the market with a viable ‘sugar cube’ thermal imaging core. Other 12um pixel based cores had been built, but this was the first affordable miniaturised thermal imaging core to be generally available to the public. Early adopters of the Lepton core noted the increased noise present in the imaging but at the original 80 x 60 pixel resolution the applications for the technology were less demanding and so the noise was less of an issue. As resolution was increased the 12um pixel based cores moved into more demanding roles where their higher noise levels were far more noticeable to the user. The 12um pixel was still showing its disadvantage in terms of signal to noise ratio at the front end. There is only so much that software processing of the images can achieve, especially in some embodiments of the technology in relatively low performance or generic computing platforms such as mobile phones. The technology needs further development before it can truly compete with the Microbolometers that use much larger pixels.OK so I hope I have set the scene with the above commentary on the 12um pixel based LWIR Microbolometer. There is no doubt that the smaller pixel size is desired by the fabrication houses, OEM’s and many end users. The technology has proven to be viable but as with many things in life, sometimes compromises have to be made and limitations accepted. It would be wrong to ‘rubbish’ 12um pixel technology as the Lepton remains a marvel of miniaturisation that has enabled use of thermal imaging in many applications not able to use the larger imaging cores. The military have Lepton cores in their miniature recon drones and the core is to be found in mobile phones and other compact devices. The 12um pixel definitely has its advantages and applications.On this forum there is often discussion about which cameras or imaging cores provide the best images. I always smile when reading the comments that follow as sometimes the commentators forget to look at the wholistic ‘picture’. A core or camera may be low cost or high cost, it may be low resolution or high resolution, it may be large or it may be small, it can be radiometric or non radiometric. Those are the choices presented to us. Each specification of core will have its place in the market and be suited to a role. The Holy Grail would be a miniature imaging core with low cost, high resolution, low noise , high frame rate and an amazing F1.0 variable zoom lens system.. Sadly life just is not that kind to usI read with interest recent posts on the FLIR BOSON core that uses 12um pixels. It is certainly not a ‘cheap’ core and it has been noted that the noise present in images is higher than had been hoped. It certainly looks an impressive core on paper and is very compact. I consider it to be a bit like a Lepton on SteroidsReal World testing of the BOSON has revealed some of its limitations but, if I am honest, I expected such from a 12um pixel based core. It uses a lot of clever ‘tricks’ to produce an acceptable image for the user. Those ‘tricks’ include much digital signal processing. As any who use DSP will know, you can get some strange behaviour if you push the DSP to its limits. FLIR have done the best they can in terms of delivering a miniaturised LWIR imaging core at an affordable price that meets the needs of many applications, despite some higher noise issues. We will no doubt see further improvements in this 12um pixel based technology over the coming years. Lowering front end noise is the key to success as I have already said. The designers are up against the laws of physics though and I do not see any Microbolometer manufacturer wanting to go back to fitting Peltier elements in their Microbolometers to cool silicon and lower system noise !I hope this post stimulates some discussion of the matter. The above is just my view of the World of 12um LWIR pixels and others may have a differing view. All comments are welcomeFraser

author: Fraser
author_rank: Super Contributor
timestamp: June 02, 2019, 01:40:50 pm
content: Just to add to how some designers of microbolometers have approached the pixel thermal collection surface area challenge, even on larger pixel sizes.......The pixels in a Microbolometer are suspended above a substrate on bridge arms. These both support the pixel and provide the controlled thermal isolation from the substrate below. Efforts have been made to use the substrate as a form of thermal reflects to increase the thermal efficiency of each pixel. The active collection area of the pixel is often surrounded by ‘dead’ space taken up by the bridge arm structure and standoff between pixels. This means that the die is larger than the simple mathematics of 12um x vertical or horizontal pixel numbers. It also means that there is room for improvement on the thermal collection area front. One solution used A core that I own an researched was the use of thermal ‘umbrellas’. There were structures that are thermally and physically bonded to the pixel. The project up and out from the pixel and their thermal collection area extends out over the dead area around the pixel. The result is an increase in the thermal collection area of each pixel to improve its thermal sensitivity whilst not increasing the size of the die, yet using otherwise useless dead inter-pixel space. Cleaver thinking but sadly also an additional challenge for the Microbolometer fabricator so also likely to increase production cost and potentially lower production reliability per silicon wafer.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: June 02, 2019, 02:07:32 pm
content: For those interested, here is the paper by Leonardo DRS on the clever ‘umbrella’ absorber they developed to improve their Microbolometer performance where small pixels are in use.https://www.leonardodrs.com/media/4752/201503advanced_microbolometer_design_wp_mr-2015-04-688.pdfFraser

author: Bill W
author_rank: Super Contributor
timestamp: June 02, 2019, 06:10:39 pm
content: Quote from: Fraser on June 02, 2019, 01:40:50 pmThis is not usually the case, the detector will be a 12µm PITCH detector.As an example (not real) if you have a 1µm gap and 1µm leg structure the actual absorbing pixel is going to be 11 x 9 µm with 'legs one side' or 9 x 9 µm if the legs wrap around to both sides.In many was what we see in specifications over the last 10 years or so is that once NeTD got to about 50mK(f/1) it ceased getting better. Each technology improvement went into making cheaper (or more profitable) sensors and cameras that performed the same.Bill

author: Fraser
author_rank: Super Contributor
timestamp: June 02, 2019, 07:39:31 pm
content: Bill W, thank you for the correction. Wow, I had not realised that the 12um pixel size included the ‘dead space’ as well. I can see why Leonardo DRS wanted to increase the thermal absorber area.What continues to confuse me a little are the NeTD claims for 12um pixels that, on paper, suggest the same performance as a Microbolometer with larger pixels and yet the real world images do not appear to show this. Noise seems to always intrude on the imaging of the 12um pixel cores that I have seen. I would love to hear user comment from real world experience on this. I know it is possible to disguise higher noise levels with aggressive video processing but that is normally not without its significant disadvantages as well.Looking forward to hearing more about 12um Microbolometer/core experiences within the forums membershipIt is very likely to be the future of affordable thermal imaging.Fraser

author: Vipitis
author_rank: Frequent Contributor
timestamp: June 02, 2019, 08:20:22 pm
content: hm I got some opinions. But I also don't know more about the details of the tech to comment. Maybe in 4 years time I know a lot more. I happen to have a 25um and 35um pixel pitch core(update post when I got good news next to it). Side by side comparisons can be made once I figured it all out.A 25um 320x240 core should have about the same area as a 12um 640x480 the radiation that reaches the sensor is the same given the same lens. However the small pixels do have increased resolution. You are splitting every pixel into four of about equal area. If you bin pixel in 2x2 format on the 12um sensor. The result should be equivalent to the larger pixels in terms of signal. Individual pixels have a smaller size and mass and therefore lower dynamic range. This can be bypassed by the more modern ROIC for sure.Substrate can also be part of this discussion. And 12um isn't even the smallest pitch. DRS does 10um LWIR cores for military only.I had the chance to talk to PhaseOne and asked about increasing resolution on the same sized sensor. Smaller pixels are the answer but the light that reaches the pixels was equal as they moved to "CMOS BSI" where no wiring blocks light. For visual cameras it is the idea of "deeper pixels" that sparked a meme on Apple. But you can see it in phones where tiny sensors with 19MP are used. I believe that smaller pixels are better. But sensor size has to be thaught about as well. A smaller sensor enables all those smaller packages and cheaper production ways. However it does reduce the DoF and makes an image narrower. For certain applications a big sensor is preferred. If we don't see products that go beyond VGA resolution with small pixels we don't gain anything in my mind.I would prefer a 12um 1280x960 sensor over a 25um 640x480 given that the same optics basically give you an equal fov. However, nobody built such a core for us to use.

author: bap2703
author_rank: Regular Contributor
timestamp: June 03, 2019, 12:20:48 pm
content: Don't know about a 1280 version but BAE makes up to 1920*1200@12um.

author: Bill W
author_rank: Super Contributor
timestamp: June 03, 2019, 12:53:13 pm
content: Quote from: Fraser on June 02, 2019, 07:39:31 pmFixed pattern or random noise Fraser ?Random noise could be the use of smaller aperture lenses to keep a useful depth of field, the NeTD using an f/1 of course.Also if dynamic range is an issue, you could have 'NeTD settings' vs what could work in a real world camera.Bill

author: cnxunuo
author_rank: Regular Contributor
timestamp: June 03, 2019, 01:52:13 pm
content: In my opinion, LWIR using QWIP or SLS are taking away most of the R&D resources, not uncooled ones. So their DSP algorithm isn't as good as I hoped, I can do significantly better using MATLAB with primitive image processing algorithm, therefore I am quite disappointed.Also take a look at what people were using 20 years ago ....I am very unpleasant to see what performance we have today with uncooled cores.I own a cooled 640*512 MWIR core, it has far better SNR, but it's still MWIR, not as good as the image gets from a LWIR imager for room temp stuff. I used to use some SLS lwir cameras in China from my school, which is a whole new world I think.

author: eKretz
author_rank: Frequent Contributor
timestamp: June 03, 2019, 02:32:36 pm
content: Larger pixels is pretty much always going to produce less noise, all other things being the same in terms of lens:detector area ratio etc. Visible light cameras are exactly the same. I have an 8MP Canon dslr that produces WAY cleaner images than my camera phone for instance. As they make progress with sensitivity, noise reduction and other factors, I'm sure a point will be reached where it won't hurt the quality of the image so much to use smaller pixels.

author: Ultrapurple
author_rank: Super Contributor
timestamp: June 03, 2019, 03:03:05 pm
content: Thanks Fraser for a very interesting and thought-provoking post. It prompted me to a stream-of-consciousnesses type response. Sorry if it's a bit incoherent...I have an interest in visible light photography, where the general thrust is "bigger pixels = better picture". That's why you can get so-called 'full-frame' DSLRs with frighteningly expensive ~36x24mm sensors, less-expensive 'APS-C' ~24 x 16mm, tiny little phone cameras and, at the other end of the spectrum, so-called 'medium format' of ~54x40mm or even 'large format' with anincredible 280x229mm (11"x9") sensor- a snip at US$110,000 for the base model. That is a 12 megapixel camera, with each pixel 75µm square. Compare that with the 8.42µm square pixels of my 12Mpix Nikon D700 35mm full-frame, the 4.35µm square pixels of the Nikon D850 45Mpix full-frame, or the 1.1µm pitch of the 23Mpix camera in the Sony Z5 Premium phone. That's quite a range of sizes to consider.All other things being equal, we know that a full-frame DSLR gives better pictures than a mobile phone. It's partly down to the difficulties inherent in trying to produce a well-focused image on a tiny sensor (diffraction tends to make this hard), but also down to sensitivity: mobile phone cameras struggle in low light and get extremely noisy as the ISO climbs into three figures; a D850 will produce perfectly usable images at ISO 10,000 (and, arguably, cellphone quality images at ISO 100,000). Capture area of the lens is also a big factor in all of this of course. We can reasonably assume that the noise per square unit of a silicon sensor is comparable irrespective of the sensor's physical size. A small sensor necessarily requires a physically small lens - the one on my phone is about 3mm diameter, whereas my DSLR lenses are generally in the region of 60mm diameter. From the same scene, then, the phone captures a light fraction of pi x 3mm square = about 10, whereas the DSLR lenses have a relative capture area of pi x 60 square = about 11,300. But to truly compare sensitivities you need to drill down further and analyse what proportion of that relative amount of light reaches each square area of sensor ... and so the calculations go on.One thing that DOES stand out, though, is that the pixel sizes are large compared to the wavelength of light. Even the smallest pixels, 1.1µm, are roughly two wavelengths square (assuming 550nm green light). For a LWIR camera, then, the equivalent of a cellphone camera would be 10µm (ish) wavelength, so pixels about 20µm square. That's not too far off the 17µm we all know and love (and I note what has been said about pixel pitch not being the same as functional detection area).On the face of it, then, 12µm pixels look as though they're pushing the physics a long, long way. The demands on the lenses too will be significant: do not underestimate the difficulties of producing a 'colour'-corrected lens that gives minimum distortion over a 2:1 wavelength range. I don't know whether it's physically possible to design a large aperture achromatic or, preferably, superachromatic lens at LWIR, but you need something of that order for best possible image quality. In visible light photography it is generally the case that the larger the sensor area, the less well-corrected the lens needs to be. On a large-format camera you only need a few lines per mm from the optical system (a 280mm wide sensor at 10 line pairs per mm gives something like 2800 pixel resolution; for the same image quality on a 36mm-wide 'full frame' camera the optical system has to deliver 2x2800/36 = about 150 line pairs/mm). I'm too frightened of big numbers to even begin to work out the optical performance that would be necessary to get the same quality on a cellphone-size sensor.Overall, then, it's not just the physics of the sensor surface that affect image quality as the pixel pitch reduces. Higher and higher demands will be put on the optics and, as has been mentioned, the digital back-end that has to try and produce a usable image from all the mush and noise it's presented with. But image processing is getting seriously clever these days - I believe there's even a system that uses artificial intelligence to make up missing data so one can 'restore' an original image after it has had text printed over it.On a quite separate note, I remember seeing somewhere an interesting ultra high resolution thermal imaging system that was based on a completely different principle from the microbolometer-type focal plane array we're used to. You may be aware that some X-Rays are made using a special re-usable 'film' that is 'read' by exposing it to a certain wavelength of light, whereupon it fluoresces a different colourin proportion to the X-Ray irradiation it has received. The film is 'reset' by exposing it to broadband light, eg normal room lighting. I saw something similar done at LWIR, where some kind of substance was applied to the item under test then (flash) exposed to a specific wavelength of light, whereupon there was a glow whose duration (and possibly intensity) was proportional to the temperature. The interesting thing about this was that the ultimate 'pixel' resolution was much closer to that of visible light, rather than LWIR light - an improvement of well over an order of magnitude. ('Pixel' is not the right term here, but it conveys the general meaning). It's interesting to consider what might be done if a high sensitivity version of that system could be developed and applied to a flat substrate - for example, a normal visible light CMOS imaging sensor. It might then be possible to have multi-megapixel thermal imagers that don't rely on microbolometers.Just sayin'...

author: bugi
author_rank: Regular Contributor
timestamp: June 03, 2019, 03:30:31 pm
content: Quote from: Ultrapurple on June 03, 2019, 03:03:05 pm(Emphasis mine.)Not quite so. One could have larger diameter lens on a tiny sensor. Or a tiny lens on a DSLR. The latter doesn't usually make much sense, though. But, as examples:For full frame DSLR, the front lens aperture is about 19mm, still F/2.8:https://www.canon-europe.com/lenses/ef-40mm-f-2-8-stm-lens/For a mobile phone, attaching big lens with an adapter:https://www.digitaltrends.com/photography/cinematic-international-smartphone-dof-adapter/More practical examples are all those mobile snap-on lenses, which are often quite a bit bigger than the phone's own lens.Granted, some combinations will not be perfect matches, but even theoretically speaking, if the optics happen to be suitable for it, nothing prevents imaging with a tiny sensor through a massive telescope. Though might not always make much sense this way, either. But, still, a less extreme example:https://youtu.be/T_YWmwAPGcw?t=93(EDIT: just to clarify, using an adapter to attach a lens to a mobile phone, which still has its own tiny lens in it, does not change things; one _could_ make camera system that has huge lens with a tiny sensor. It is just that everyone already has their own tiny sensors in the phones, so the adapter-way is practical and cheap.)

author: cnxunuo
author_rank: Regular Contributor
timestamp: June 03, 2019, 04:29:41 pm
content: From my experiences, visible light is a whole new story with much advanced science and image processing involved.I own a lots of medium format digital back as well as full frame entry level camera such as a7r3 a7s2, a9. 10 years ago, bigger format seems important, but nowadays, image processing is 90% what makes a clean low noise picture given that you have a moderate sensor.In my comparison, a 400MP (100MP sensor) or a similar sized 150MP sensor (phase one IQ4) produce lower SNR compared to old a7r3, not because of their sensor is worse, in fact it's pixel pitch is actually bigger than Sony, it's their image processing DSP can't even compete with modern cellphones let alone Sony mirror less, which has extremely good denoising software BEFORE RAW file, this means your raw file is not the sensor performance, but a result from its DSP. That's why Sony RAW file seems so impressive...Phase one gives you 3f file, which is before debayer, but Sony only give you the proccessed denoised and sharpened image in RAW format, which is cheating, so I mainly shoot film. A velvia in 8x10 or 4x5 beats every consumer digital in the worldThats why I am so disappointed by flir boson 640, they didn't even try to make it's DSP good.....It has a complete dissaster level image processing and calibration flow, but fortunately with its 16bit raw output, I can always do my DSP in post processing.

author: Fraser
author_rank: Super Contributor
timestamp: June 03, 2019, 08:21:57 pm
content: cnxunuo,It was actually your posts on the BOSON that lead to me creating this post. I was surprised at your experience with the BOSON so wondered whether the 12um pixel pitch is the issue. Your comments on the signal processing are VERY interesting. FLIR have historically wanted to improve their image processing software within the cameras and spent resources on such. The various generations of FLIR industrial thermal cameras since 1997 have incorporated ever improving image processing. I would have expected the BOSON to have some pretty advanced image processing to make it appealing to the military, an obvious market for it. I expected the Lepton to be a compromise solution, but not the BOSON.Fraser

author: cnxunuo
author_rank: Regular Contributor
timestamp: June 03, 2019, 10:49:20 pm
content: Hi Fraser, I also couldn't believe how bad the algorithms is , since it's not a shutterless NUC , it shouldn't behave like this. Each time the calibration shutter kicks in, both automatically and manually demanded, different random horizontal and vertical patterns showed up, even if I set it to 16 frame average in their software. This is clearly some serious mistake or more like a deliberate add-in since a simple one frame subtraction can easily remove those lines. The noise is although within spec, but way worse to the eye as peak-peak value is too high.https://www.eevblog.com/forum/thermal-imaging/noise-reduction-on-flir-boson-640/My own confirmation with post image processing (nothing fancy, really basic) are in the URL above. I really hope they could fit a better lens to it too, the lens is only sharp in the center, as they designed it very tightly for small image circle in order to save some germanium, the corners are weird and blurry, not too bad but definitely noticeable and I really hate it when doing panorama stitching.

author: cnxunuo
author_rank: Regular Contributor
timestamp: June 03, 2019, 10:58:37 pm
content: Their mil stuff (which I shouldn't know but from openly available PDFs) indeed has algorithms which is considered advanced for its day, such as local histogram equalization for added detail in varying contrast scene, and tricks to make the noise seems less distracting in their EO systems,however the Boston's output is meant to be radiometric, you can't arbitrarily modify contrast and sharpen images, which non of those algorithms for boosting visual details can be applied, so I don't blame them for not having the best 'visual appearance' algorithms. It's their NUC, their randomly accruing patterns that I believe needs improvement. I already did many many in camera calibration for gain (using cold and hot blackbody), lens uniformity, and every calibration I can access with their software, non of them makes it better. So I am planning to use it without it's calibration DSP but simply stream 16bit video and I do the corrections afterwards.

author: Fraser
author_rank: Super Contributor
timestamp: June 04, 2019, 12:12:54 am
content: cnxunuo,Thanks for the excellent comments. I am also reminded of the very regular FFC flag operations on the Seek Thermal classic camera. It seemed the Microbolometer was very thermally unstable, or that was the design teams concern anyway. Never before had I seen such a short period between FFC events on a camera once it was at nominal operating temperature.I am also wondering about the structure of FLIR R&D these days. I have no inside knowledge but I can say how things used to be....FLIR bought AGEMA who were a leading manufacturer of cooled thermal imaging cameras for professional and Government customers. Their cameras were highly regarded in industry. A competitor in the thermal imaging market was Inframetrics. They also had an excellent reputation in Industry for producing very capable cooled cameras. FLIR bought them as well ! So FLIR had two serious players in the thermal imaging industry under their company banner. Not all AGEMA or Inframetrics employees were very happy about this change though ! That is another story though. FLIR had some VERY clever and capable specialist engineers at their disposal. AGEMA had already designed and produced an uncooked Microbolometer thermal camera in the form of the Thermovision 570. It was hoped that the Microbolometer Thermovision 570 might appeal to customers of the cooled Thermovision 550 but the higher noise levels in the 570 units images were very noticeable when the cameras were compared side by side. The 570 offered lower cost of ownership, a lower noise profile and greater reliability than the cooled 550 but it could not compete on the quality of images produced. The generations of PM series cameras that followed were all FLIR badged but designed by the old AGEMA team in Sweden. They kept improving the Microbolometer noise performance and image processing software in a continued attempt to bring uncooled (but temperature stabilised) Microbolometer based cameras closer to the performance of the THV550. The PM695 was the last of that series of cameras and offers the user a choice of noise reduction configurations to suit differing tasks. Whilst the highest level of noise reduction is very effective, it appears to be stacking frames and so is a poor choice for moving targets or when the camera is not on a tripod. Smearing occurs ! FLIR were intent on getting the best possible imagery out of their industrial thermal cameras and the new models of professional and Industrial cameras that followed the PM series maintained the development in noise reduction and processing. At the end of the day though, the Microbolometer is a very noisy and unruly sensor. It has many ‘bad habits’ and needs to be tamed with clever tricks of the trade. In comparison the cooled FPA cameras had a ‘darling’ sensor that was temperature stabilised, very low noise, predictable in behaviour and well understood.FLIR turned its eye towards companies familiar with uncooled imaging technology and bought in the knowledge that the AGEMA and Inframetrics designers did not have. This was when Indigo and Extech were procured. Those two companies produced compact uncooled thermal imaging cameras and this appealed to FLIR as a way forwards in their business beyond just larger industrial and professional thermal cameras. Indigo had a lot of experience designing very capable and compact uncooled Microbolometer based imaging cores. Their in depth knowledge was invaluable to FLIR. Not all employees of Indigo were happy about being acquired by FLIR though. The Indigo Microbolometer core technology was quickly embraced by FLIR. Indigo had the Omega and Photon cores that were field proven and further development under a FLIR banner lead to the popular TAU series of cores. This was a completely different development team and work stream to that which had designed the PM series cameras and those Industrial cameras that followed.The compact Microbolometer imaging cores that we now see in the FLIR product inventory are effectively just developments of Indigo designs and very likely the same designers behind them. I suspect that the Lepton and BOSON have the same design team. That team may have a different approach or view on dealing with the noise and somewhat unstable behaviour of the Microbolometer when compared to the design team behind the higher performance Industrial cameras. It could be that we are effectively looking a two distinctly separate ‘design companies’ working under the common FLIR banner. Indigo were experts in miniaturisation but may not have been so experienced or effective in noise reduction techniques, especially when dealing with more challenging Microbolometers like those that use 12um pitch pixels.It should not be forgotten that a leading light from Indigo who had much experience in the design and development of cooled thermal cameras, left FLIR to create the company called SEEK Thermal. His aim was to produce a more affordable thermal camera ‘for the masses’. A most laudable objective. The SEEK cameras tend to have some issues with noise reduction though. Could this be a sign that even the experience gained whilst at Indigo was not enough to overcome the challenges of the new 12um pixel pitch microbolometers ?Just food for thoughtFraser

author: Ultrapurple
author_rank: Super Contributor
timestamp: June 04, 2019, 08:07:06 am
content: Quote from: cnxunuo on June 03, 2019, 10:49:20 pmBy chance I was reading today about recent designs for visible light camera lenses. Broadly speaking, the writer claimed that many newly-designed lenses for modern DSLR and, particularly, mirrorless cameras have a considerable degree of falloff (darkening) at the corners that is compensated for quite aggressively in the camera software. It's easily done - progressive gain, 'binning' pixels together to lower noise at the cost of resolution in a part of the image where the focus won't be sharp anyway, and I'm sure there are other techniques. The point, of course, is that you can use smaller (=cheaper) lens elements if you don't need to produce quite such a large, distortion-free, unvignetted image circle.I suspect something similar may be afoot with thermal imaging systems. Most of the time you're only interested in the central portion of the image, so what does it matter (runs the thought process) if the corners are a bit noisier, or maybe have some frame averaging, or whatever - particularly if it means the manufacturer can sell its product for less than its competitor.I am aware that FLIR (et al) have poured a great deal of money into image processing research. I'm sure the visible light sensor giants (Sony, Canon, Nikon...) have done so too, and everything is probably sewn up in patents. I wouldn't be surprised if there was some cross-licencing going on, as many of the basic principles are closely allied (even if the sensors work on different principles).

author: cnxunuo
author_rank: Regular Contributor
timestamp: June 04, 2019, 10:12:56 am
content: Premium lens for mirror less, are the opposite. Such as otus 55mm 1.4, is actually a medium format wide angle lens, but the full frame only uses it's center portion, therefore getting a edge to edge sharpness, with no visible fall off.It's not something new, just an aggressively expensive and heavy weight design for a small market which no one bothers to do some years ago.Back in the 2000s, 640 25um lens has a huge image circle margin with no visible fall off too, I think it's flir cutting down it's cost and shows less respect to them, as lwir was an expensive and premium thing 15 years ago, they pay much more respect to lens choosing of performance over profits.

author: Fraser
author_rank: Super Contributor
timestamp: June 04, 2019, 10:26:58 pm
content: An interesting article that also touches on the technology used in the Boson design.https://www.engineering.com/AdvancedManufacturing/ArticleID/18429/Infrared-Innovation-Developing-an-Affordable-Portable-MWIR-Infrared-Imaging-Solution.aspxFraser

author: Fraser
author_rank: Super Contributor
timestamp: June 04, 2019, 10:34:43 pm
content: 12um pixel pitch microbolomter development paper from 2013. Some interesting comments on improving the efficiency of the small pixel........Quote....Uncooled infrared detectors with 12μm pixel pitch video graphics array (VGA) have been developed. To improve the signal to noise ratio (SNR) for 12μm pixel pitch, a highly sensitive bolometer material, an advanced pixel structure for thermal isolation and a newly designed read-out IC (ROIC) have been also developed. The bolometer material has been improved by using vanadium niobate. Over a wide range of temperature, temperature coefficient of resistance (TCR) is achieved higher level than -3.6%/K, which is 2 times higher than that for the conventional bolometer material. For thermal isolation, thermal conductance (Gth) value for the new pixel structure, fabricated by using triple level sacrificial layer process, is estimated to be 5nW/K, which is 1/5 times lower than that for the conventional pixel structure. On the other hand, since the imaging area is reduced by the pixel pitch, the uniformity of pixel can be improved. This enables to remove the non-uniformity correction (NUC) circuit in the ROIC. Removal of this circuit is effective for low power and low noise. This 12μm pixel pitch VGA detector is packaged in a compact (24 × 24 × 6.5 mm) and lightweight (11g) ceramic package. In addition, it has been incorporated in a newly developed prototype miniature imager. The miniature imager has dimension of 25(H) ×25(W) ×28(L) mm and weight of 30g. This imager is compact and small enough to fit in your hand. Hereafter, this imager is greatly expected to be applied to mobile systems........UnquoteFull paper is available here.....http://spie.org/Publications/Proceedings/Paper/10.1117/12.2013690Fraser

author: Fraser
author_rank: Super Contributor
timestamp: June 04, 2019, 10:42:09 pm
content: A paper on Microbolometer technology that may prove interesting to some readers. It discusses noise types etc. It is quite an old paper from 2004 but the issues details remain relevant for modern Microbolometer designs as well.https://user.eng.umd.edu/~neil/RT/MSEEfinalcopyB.docFraser

author: Fraser
author_rank: Super Contributor
timestamp: June 05, 2019, 11:37:50 am
content: An interesting SPIE paper for those with access.https://www.spiedigitallibrary.org/conference-proceedings-of-spie/8355/83550O/Infrared-detector-size-how-low-should-you-go/10.1117/12.919951.fullpdf?SSO=1It is often possible to read such papers for free if you know where to lookA search on the term “Sci Hub” can prove interesting.In the papers summary it is stated that that the minimum size for a LWIR pixel is likely to be 5um and for MWIR it is 3um. Interesting readingFraser

author: Ultrapurple
author_rank: Super Contributor
timestamp: June 06, 2019, 09:20:15 am
content: That paper contains some very interesting food for thought, Fraser - thanks for finding it.I do rather like the idea of a 4k resolution dual band (LWIR and MWIR) sensor half an inch square - not that they're saying it's feasible yet, but it's very interesting to see the thinking going in that direction. Optics for such a system would be interesting: a stable lens that keeps everything in good focus from roughly 3-14µm would probably be a challenge!At shorter wavelengths, there are a very few camera lenses that manage NIR to UV, for instance the rareUV-Nikkor 105mmis specified from 1300nm to 190nm (a comparable range to that required for the IR sensor discussed) and, in modern form, costs about US$7,500 new and over half that for the original lens in good used condition. (The mechanically-similar but optically very different regular 105mm f/4 from the same era is about US$200 near-mint used).

author: Rerouter
author_rank: Super Contributor
timestamp: June 06, 2019, 09:30:47 am
content: They could also make use of the image processing smart phones are starting to use. Relying on the camera not being perfectly held still and using the drift to correlate out noise across nearby pixels.

author: Fraser
author_rank: Super Contributor
timestamp: June 06, 2019, 09:45:40 am
content: There is definitely room for improvement on the image processing front. With image processors getting more powerful by the year, the thermal imaging industry needs to step up and embrace the latest technology and associated software. In my opinion, the weak area of the thermal imaging industry was, and still is, the software side of the designs, be it in the camera or the external computer image analysis and post capture processing. When I first saw Researcher 2.8 I thought “is this it ? Really ?” It was very ‘old school’. Historically the image analysis software for industrial thermal cameras has been way behind that found for visible light work. ResearchIR 4 is better and heading in the right direction. By no means perfect though ! I found similar ‘dated’ software, firmware (call it what you will) in thermal cameras. The Microbolometer May be bleeding edge technology, but the software running on the embedded computers is far from it.As has been said, maybe some clever ideas from the mobile phone camera image processing world will migrate across to thermal camera software. The quality of image that can be captured on a decent mobile phone is quite amazing considering what actually collects the image data ! Nowhere near the quality of a DSLR I know, but still surprisingly good with such a small sensor and lens system. The low light performance of my humble iPad Air 2 never ceases to surprise me.Fraser

author: Rerouter
author_rank: Super Contributor
timestamp: June 06, 2019, 10:21:12 am
content: Not sure if anyone wants to try and make an implementation, no neural networks,https://sites.google.com/view/handheld-super-res/

author: cnxunuo
author_rank: Regular Contributor
timestamp: June 06, 2019, 11:04:33 am
content: Quote from: Ultrapurple on June 06, 2019, 09:20:15 amwow didn't expect to hear someone mentioning such a rare lens on a thermal imaging blog post....A UV-nikkor or UV-sonnar for blad, or the Coastal Optics 60mm which I like the best, all uses fluorite for APO, there's no fluorite to glass substitute for germanium unfortunately, but they already used "Diffractive Optics" mainly to save cost but also improve APO from 7 to 13um, as in the boson lens, there's ring pattern view from the front lens element. but it's still already quite good compared to its wavelength, can't defeats diffraction at the end. let's hope they wont cut down the cost of lens even more aggressively, perhaps better to get back to the tau or photon days....

author: Max Planck
author_rank: Regular Contributor
timestamp: June 06, 2019, 05:33:44 pm
content: Quote from: Ultrapurple on June 06, 2019, 09:20:15 amSuch lenses are available COTS.Regarding FPAs wit 12um pixel pitch, just a thought. There is probably a reason why FLIR is using in their newest OGI camera - GF77 - a FPA with 25 um pixels.Max

author: Hydron
author_rank: Super Contributor
timestamp: June 06, 2019, 07:06:05 pm
content: Inspired by this thread I dug out a 320x240 Boson we had at work to have a look - not pretty when comparing it to a Tau2! Much better if you want to stick it on a small drone or something though.

author: Fraser
author_rank: Super Contributor
timestamp: June 06, 2019, 08:02:22 pm
content: @Hydron,This is why I started this thread. I was so shocked and disappointed that the BOSON appears to be a flawed thermal imaging core when I had expected it to be the darling of the drone fraternity and military users. Make no mistake about it, the military want and need miniaturised thermal imaging cameras on the modern battlefield and intelligence gathering operations. If the BOSON turns out to be a ‘damp squib’ FLIR will have suffered a serious setback to their plans. The TAU series remains a superb core that is well ‘sorted’. Not as good as the cores running in FLIR industrial cameras but very good all the same. The TAU is perfect for night vision applications and scopes, be they observation or weapons sights. The BOSON should have taken the miniaturisation of the cores to the next level without noticeable loss of image quality and performance. That does not currently appear to be the case thoughFraser

author: naze
author_rank: Newbie
timestamp: June 11, 2019, 02:25:23 pm
content: 12um pixel size is still having distance to physical limit: in order to detect LWIR up to 14um wavelength, pixels cannot be smaller than 7um.