I want to buy additional lenses for my Boson 640. What lenses are compatible?

[therwp]

I own a Boson 640 (60 hz, <40 mK sensitivity) that came with an 8.7mm FLIR-branded lens. FLIR offers the Boson 640 in configurations with 73mm, 55mm, 36mm, 24mm, 18mm and other size lenses.

Jiangsu Ascendent Optronics sells a variety of thermal lenses, as do many other manufacturers, but I have no idea whether lenses are compatible with (a) the camera, and (b) the existing threading and mount.

See, e.g. https://jaoinc.en.alibaba.com/productgrouplist-805942511/Thermal_lens.html

What do I need to look for to ensure compatibility?

Similar story with my Therm-App Pro 640x480 thermal camera. For that camera, I own a 35mm lens and the stock 19mm (I think) lens, but I would like to purchase other lenses. No idea what to look for, though.

[Fraser]

Things to check when buying a lens......

1. Mount diameter
2. Mount thread pitch
3. Back-focus distance of current lens
4. Back-focus distance of other manufacturers lens
5. Illumination circle of the other manufacturers lens - is it suitable (large enough) for your resolution and pixel size ?
Lenses are often listed in tables where the field of view is stated for different resolutions and pixel sizes. Some lenses can illuminate a 320 x 240 12um pixel microbolometer, but not a 640 x 480 12um pixel microbolometer due to the image circle size at the rear of the lens. Look at the lens specification sheets and any ray plots that are provided to better understand what another manufacturers lens will behave like on your camera.

If fitting a different lens to your camera, it is normal practice to carry out a fresh calibration with the new lens to ensure a decent flat field and radiometric accuracy.

Note that all lenses are not made equal. A "cheap" lens that may perform adequately on an older 160 x 120 50um pixel camera may not perform to an acceptable level on a modern 640 x 480 12um pixel camera. The low resolution of thermal imaging microbolometers is quite forgiving of lens quality, but there are limits to what you can get away with.

In some cases it is necessary to make lens mount adapters if a camera uses a non standard mount thread. In such cases, care is needed as the back focus distance  dictates how far away the lens can be from the microbolometer.

From memory, Therm-App uses a standard Ophir lens so the lens mount is known. I attach a picture and the 19mm lens datasheet from Ophir's catalogue. Not cheap lenses though. The datasheet shows you what I mean about back focus distance etc.

Fraser

[Fraser]

I just found a note saying that the Therm-App uses a 25mm x 0.5mm threaded mount.

No idea what the Boson uses but that data may be available via FLIR's documents or a direct question to their customer support

Fraser

[Vipitis]

I do remember a few things from exploring that path. As per boson documentation you can save exactly two lens calibration profiles in the camera directly and there is an option to swap between them with some control software. The documentation also states that you are only supposed to change lenses in a clean room to avoid dirt or breaking exposed bond wires.

So that makes it really difficult go change lenses in the field. There are OEM solutions that include zoom lenses which are really expensive. And I even saw one example that made use of a lens turret to change between lenses easily.

Contact the sales people of whatever lenses you decide to buy and just ask them about compatibility with your Boson 640

[svgurus]

Your boson has m24*0,5 lens mount, it is similar to one of flir tau, you can find some lenses from it on ebay. Chinese usually have m25*0.5 or m34 mounts. afaik 0.5 in flir differs from 0.5 in thermapp/chinese, lol, get ready for surprises and experiments. tau has bigger case and shutter so i guess you wont have problems with back working distance but chinese make really different and odd lenses) i have 35 1,2 and 50 1,0 from them with m25 thread
and yeah, that lines from boson datasheet about changing lenses and quality tolerances bother me too, you need it for UAV or just thought it is small and classy?)
about TA pro - i have usual TA, chinese m25 lenses fit it perfectly. wider ones might be not capable of covering vga resolution though