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IR cam close focus

I was looking for long for an IR cam and finally got one at a pretty good price (FLIR Thermacam B2).

I previously borrowed several other models and always have been not satisfied with the resolution. 120x160 was OK, but working with 0201 size I could barely see them components: they invariably focus down to only slightly better than 10cm and I didn't want to pay the huge extra for the long focal additional lens.

Now the one I've found, despite the advertised 10cm focus range, can go waaaay lower and I can easily fill the image with a 7mm sensor board I designed some time ago. That's really nice and I very pleased with it.

Now I just wonder what is the price to be paid in loss of accuracy when focusing closer than the specified range. Here I'm thinking of impact of internal reflections, reflections of the camera internal IRs onto the PCB (the cam obviously is not a cooled one) and such...

Thanks,

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Thanks,
Fred.
Reply to
Fred Bartoli
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For calibration and internal reflections, try focusing in close on a thick piece of aluminum painted black and held at a known temperature or two (the aluminum will keep the temperature constant across the target, the blackness will keep external reflections down). If you have narcissus or internal reflections at close focus you'll be able to see it (sometimes you can recognize parts). You may also find that the calibration is different from the middle of the view to the edge.

You'll always get some external narcissus when you focus on a flat plate. Having an uncooled detector is actually better in this case than a cooled one: look in a mirror with a cryogenicaly cooled FLIR and there's this deep black spot in the middle of the image. If your PCB is relatively high emissivity these external reflections shouldn't be a problem: emissivity is the reciprocal of absorption, so a high-emissivity surface will absorb whatever is coming out of the camera.

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Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
Reply to
Tim Wescott

We have an E2 with the "wide angle" germanium lens. This lens is radically curved, practically a hemisphere. We can essentially touch a part with the lens and be in focus. We can resolve the hot-spot temperature in the middle of an 0603 resistor.

These are 0805's:

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We could have got closer. The kapton tape has an emissivity close to

1, so gives us a good indication of the temperature of the copper foil, which is practically a mirror at these wavelengths.

Here a tiny dual RF transistor, with one of the chips dissipating 80 milliwatts...

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I love this thing.

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John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
Reply to
John Larkin

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