Field of view, smallest recognizable object and measurement spot
The field of view (FOV) describes the area visible with a thermal imager. It is dependent on the lens used. Wide-angle lenses are suitable for large fields of view, telephoto lenses for good spatial resolution. The larger the field of view, the more you see. Especially when using the thermal imager indoors, a wide field of view (> 30°) is useful, as the walls only allow the user to distance himself from the measurement to a limited extend in order to see more.
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The smallest measurable object / the measurement spot (IFOVmeas)
The smallest measurable object describes the smallest object which can not only be recognized, but whose temperature can also be accurately measured. At a spatial resolution of the lens of 3.5 mrad, and a measurement distance of 1 m , the smallest recognizable object has an edge length of 3.5 mm, and is shown in he display as a pixel. For an exact measurement, the measurement object should be 2 to 3 times larger than the smallest recognizable object. As a rule of thumb, for the smallest measurable object (IFOVmeas): IFOVmeas ≈ 3 x IFOVgeo
The smallest recognizable object (IFOVgeo)
The smallest recognizable object is the smallest dimension which can be recognized by one pixel. A pixel is an element on the thermal imager's detector which records IR radiation and transforms it into electrical signals. Each pixel corresponds to one measurement value.
Find out in our compact tutorial how to turn theoretical basics and the right thermal imager into meaningful thermal images in practice.