How Many Degrees Can An Infrared Camera Differentiate

Until recently, nearly buyers of infrared imaging cameras had to make a budgeting choice between a low-resolution 160x120-pixel camera or no camera at all, but they presently learned they missed a lot at low resolution. Starting at virtually $25,000 and going upwardly from there, professional high-resolution 320x240-pixel cameras were too costly for anyone who was not a full-fourth dimension thermographer or not working for a visitor that could afford to buy expensive tools that might be underutilized.

That changed in 2005 with the introduction of cameras costing less than $15,000 that utilise a high-performance 320x240 microbolometer detector. Still, many users want to know: Why is higher resolution important in thermal imaging? Why have the professional thermographers always been willing to pay the premium for the 320x240-pixel detectors used in uncooled, focal-plane-array cameras?

Pixels are the data acquisition points for thermal measurement, and this data is used to create a visual prototype from the thermal contour.

"More data points mean more information is provided for accurate thermal interpretation. More pixels besides mean greater visual resolution in the thermal epitome. So for a given field of view, smaller details can be identified in the thermal image and accurately measured for temperature," says Jon Chynoweth, vice president of Mikron Infrared.

Chynoweth says that to make IR cameras affordable to a wider range of users, detectors with pixel counts of 160x120, with or without interpolation, were introduced as a low-toll alternative.

"But this is one-4th the resolution of the 320x240 detector: 76,800 pixels vs. 19,200," he says. "The larger detector produces an image twice as wide and twice as high, with four times the data for a given field of view."

For the working thermographer, high resolution allows a camera to work at a much greater distance from a target without loss of temperature measurement accuracy, Chynoweth explains.

"A target must embrace at least 9 pixels on the FPA to be accurately resolved, or else the resulting temperature measurement will be compromised when the photographic camera averages in inapplicable background," he says.

The lower-resolution detector interpolates a greater surface area between pixels and averages in temperature readings unrelated to the target. In practice, a target that's 0.25 square inches can be accurately measured for temperature at a altitude of 60 feet with the 320x240 detector, while the 160x120 detector has to be at thirty anxiety to ensure the same accurateness. (Distances are based on a 25-degree x 19-degree lens).

"Resolution is even more than important in infrared imaging than it is in digital photography, and anybody knows how photographers boast about the resolution of their newest digital cameras," Chynoweth says. "In infrared, resolution affects temperature measurement accuracy, not just image quality. The 320x240 detector, with 76,800 temperature-measuring pixels, resolves an surface area smaller than a 10th of a square inch at 6 feet, while the 160x120 detector, with just 19,200 pixels, can't image anything smaller than twice that size. With more groundwork averaged into temperature readings, the readings are inherently less accurate. Likewise, the low-resolution thermal paradigm looks similar it's fabricated of tiny little squares, no matter what the viewing size."

Detector Size	Number of pixels
320 x 240	76,800
160 ten 120	19,200

Target Distance	Field of View	Pixel Size 320 10 240	Pixel Size 160 10 120
(Feet)	(Feet)	(Inches)	(Inches)
one	0.38 x 0.29	0.014 x 0.014	0.029 x 0.029
half-dozen	ii.30 ten 1.73	0.086 x 0.086	0.173 ten .173
10	3.83 x two.88	0.144 x 0.144	0.288 ten 0.288
20	seven.67 10 5.76	0.288 x 0.288	0.575 10 0.576
50	19.17 ten xiv.41	0.719 x 0.720	1.437 ten 1.441

Another fine bespeak in detector pattern is fill gene – the infinite between pixels on the detector that has to be interpolated when the paradigm is formed electronically.

"The newest detectors developed accept reduced this spacing 25 pct, giving them the highest make full factor and best imaging capability in the manufacture," Chynoweth says.

The 160x120 detector epitome (top) shows a lack of definition compared to the image produced by a 320x240 detector. Temperature resolution and accuracy of the 160x120 image are proportionally less besides.