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Looking for narrow lwir lens for flir one camera

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grrrrrrr:
I am looking for a narrow lens with infinity focus for lwir flir lepton sensor . The lenses from umicore used on the therm app looks promising but out of my budget. Any diy solution? are some software out there to calculate the right optic? does the new optic can be just mounted front or does the original optic have to be removed? thanks

Bill W:
You are looking at having to replace the lens, a lot of what is discussed here is producing close-up adaptors.

At a simple level the lens requirements are just a bit of maths.  You can assume that it is a 'simple' lens and when focused at infinity the 'simple' lens must be at its' focal length from the sensor image plane.

The horizontal width of the sensor is px * pitch
px = horizontal pixels
pitch = pitch of pixels

The distance centre to edge of image for the lens is FL* TAN(HFOV/2) which must be (px*pitch) / 2
FL = focal length
HFOV = horizontal field of view

Then just rearrange the maths as necessary.  A good test case is that a 320@25um sensor needs a 9mm lens for 50° field of view.  You can scale from that scenario if you prefer.

Things are not quite this simple in reality but will give you a good start.  your most likely problem is if you are going to resolve down to the small pixels, and what distortions you get off axis.  It means that a single element lens or a lens from a much older camera may not be up to it.  I have a few 15mm f/1 assemblies if you want to try, but those were designed for 50um pitch 320 sensors.

You can hit Wikipedia to read up on 'circle of confusion' and 'diffraction limited optics'.


regards
Bill

www.fire-tics.co.uk

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