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How do I capture better thermal images?

Published:  10 October, 2018

The answer to this month’s trouble shooter is supplied by FLIR Systems.

A:

It may seem obvious, but the most fundamental requirement is getting the target in focus. It’s not just about making sure the thermal image is clear and crisp for easy identification of the stored image, if it is out of focus, temperature measurement will be inaccurate.

Make sure you adjust the temperature range to suit the application at the point of image capture too. A typical professional camera can measure temperatures from around -40 to 1500°C but needs several dynamic ranges to cover this span. Without adjustment, you won’t be able to see the thermal detail and measurements won’t be accurate.

The width and narrowness of the thermal span directly affects the thermal contrast and the distribution of colour whichever colour palette you choose. Too narrow, the thermal data will be saturated, too wide and thermal anomalies won’t be visible. Go for low contrast palettes on high contrast targets and vice versa.

All optical imaging systems reach a limit in their ability to resolve very small targets effectively and an IR camera is no different, except that as well as ‘seeing’ small objects it is also required to measure their temperature. Quite simply, the more pixels your camera has at its disposal, the further you can stand away from the target and still be able to see important detail. So, making a judgement on distance according to the spec of your camera is essential to capturing a great thermal image.

For longer distance targets, maybe use a lens with a smaller field of view, move closer or do both. And remember digital zoom only magnifies pixels, it doesn’t compensate for distance or improve measurement.

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