Article on DIY macro and telephoto thermal optics - Page 1
Forum section: electronics / general

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 08, 2018, 10:22:54 am
content: http://uvirimaging.com/2018/03/05/thermal-camera-diy-macro-and-telephoto-converters/

author: frenky
author_rank: Unknown
timestamp: March 08, 2018, 11:48:09 am
content: Nice.I have plenty of ZnSe and some Germanium lens. Will try to put something similar together.

author: Fraser
author_rank: Super Contributor
timestamp: March 08, 2018, 02:28:57 pm
content: Thanks Mike. Great spotFraser

author: Vipitis
author_rank: Frequent Contributor
timestamp: March 08, 2018, 03:42:29 pm
content: This is the first in depth article I have seen on this topic. While they used expensive housing and mounting options, 3D printing will be the cheaper and easier method for me. I belive I can undercut the 300$ for the TPL converter down to 100€ to build something that works with my current camera and potential updates I do in the future.

author: railrun
author_rank: Regular Contributor
timestamp: March 08, 2018, 04:02:37 pm
content: Quote from: Vipitis on March 08, 2018, 03:42:29 pmI wouldn’t suggest to use 3d-printed parts as a housing due to thermalisation. Otherwise you will get a nice halo effect I believe.

author: Spirit532
author_rank: Frequent Contributor
timestamp: March 08, 2018, 05:47:53 pm
content: While this is a wonderful article, the lens he proposes is extremely limiting - it will only work with tiny sensors, or will be exorbitantly expensive to source.You can already see some vignetting and halo on this Seek Reveal, which has a very small sensor. If one attempted to make a telephoto lens for something like a FLIR Exx or Txxx camera, you would be in a world of hurt, with just the lens elements blowing through $1000 right away - the point at which the original telephoto lenses can be found second-hand, or sometimes even brand new from the manufacturer.

author: nidlaX
author_rank: Frequent Contributor
timestamp: March 09, 2018, 03:54:34 am
content: Tiny image circles on these lens setups...

author: Uho
author_rank: Frequent Contributor
timestamp: March 09, 2018, 07:24:58 am
content: The lens inverts the image. I have not read anywhere how he solved this problem. It is solved, but who does not know about it will waste money on expensive lenses...

author: Fraser
author_rank: Super Contributor
timestamp: March 09, 2018, 10:24:24 am
content: There is normally a need for carefully positioned diaphragms or baffles within the lens barrel, plus a coated interior to reduce internal reflections. This is especially so in Keplerian telescope designs. There are also narcissus effects to be considered.It should also be noted that many CO2 Laser cutter lenses are not actually intended for image processing. Distortion will be present. Manufacturers state that they are intended for NON Critical applications where imperfect optics are acceptable. When buying lenses, check that they are intended for image processing tasks and not just laser collimation. Such will also be clear from the price. Image processing grade lenses are far more expensive than the standard laser collimator lenses.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: March 09, 2018, 02:16:19 pm
content: When experimenting with DIY lens designs I tend to look for complete lens solutions that I can adapt to my needs. In this case I would look for a nice zoom or telephoto C Mount lens from China. I would extract the optical glass and use the lens tube as the mount for my Germanium or ZnSe lenses. Obviously some level of adaption is required, but still easier than starting from scratch and much less expensive than buying all the lens tube parts from Thorlabs (in the UK at least).An example of a Chinese Close up lens for a video microscope is to be found here for just £16 ...https://www.ebay.co.uk/itm/8X-100X-55mm-290mm-C-mount-Zoom-Glass-Lens-for-Industry-Lab-Microscope-Camera/231989778579?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649A good starting point for experimentation, or even the finished lens assembly. A 3D printer is useful for making lens element mounts within the tube and any other custom parts needed. The standard C mount output opens up the options for connercial lens mount adapters and also provides a decent pupil size for larger lenses thermal cameras. Why reinvent the wheel when you can adapt an affordable design from China?

author: Fraser
author_rank: Super Contributor
timestamp: March 09, 2018, 02:26:02 pm
content: Regarding athermalization..... for those unaware, this is the issue of maintaining the correct separation distance between lens elements over a range of temperatures. Expansion and contraction of the lens tube with temperature can change the set distance and effect the performance of the lens.We are considering afocal lenses in this thread, or at least that is what is shown in the article. As such, it is important that the lens is configured for correct focus. I personally would include a small amount of manual focus capability in the lens design. A professional lens is carefully designed with automatic temperature compensation to maintain correct lens distances throughout a range of temperatures. Such can involve the use of specific materials in the design. For DIY projects, it may be enough to just have some focus fine tuning available. We must remember that we are working with relatively low resolution images and either fixed or manual focus lenses on the camera. The spectrum covered by the lens and camera also Introduces wavelength issues when it comes to optimum focal points. For our needs, close enough is often good enough

author: Vipitis
author_rank: Frequent Contributor
timestamp: March 09, 2018, 05:11:54 pm
content: I think about picking up a whole set of an optical test bed, with various mirrors and glass elements. I will add Ge and ZnSe elements in the future.http://www.helmut-singer.de/imgg/optiksortiment2.jpg

author: Spirit532
author_rank: Frequent Contributor
timestamp: March 09, 2018, 09:03:30 pm
content: Quote from: Fraser on March 09, 2018, 02:16:19 pmI highly recommend this for experimentation. If you only need a lens focusing system, it's a good alternative to the more expensive Thorlabs variant.I have one, and what you get is basically a single-element stage(macro lens) moving inside a loooooooooooong(over 5cm), super-smooth(sometimes even too stiff) captive helicoid, with enough space to mount an additional back AND front element if you desire(making a 3-element lens).The diameters are slightly different, but with some cheap cardboard or something like that they will fit regular laser focusing lenses. However, the carriage that moves the macro lens has a very tiny opening which will either need to be drilled out by hand(crudely) or turned open on a lathe. Not difficult to do, but is a requirement.I've acquired some optical simulation and design software, will soon attempt making at the very least a Keplerian teleconverter, though hopefully a Galilean one is possible as well(just need a plano-concave lens).