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5.6. Lens and Imager Field of View
This table lists the horizontal FOV, vertical FOV and IFOV for the lens.
IFOV (Instantaneous Field of View) is the smallest detai within the FOV that
can be detected or seen at a set distance, the unit is rad.
The formula is this:
IFOV = ( Pixel Size )/ ( Lens focal length ) ;
D:S
theoretical
= 1/ IFOV
theoretical
) is the calculated spot size based on
the pixel size of the Thermal Imager detector array and lens focal length.
Example: If Thermal Imager uses 9mm lens, because the Pixel Size of
detector is 34um.
Horizontal FOV is 21°, Vertical FOV is 21°, the IFOV is 34um/7.5mm =
4.53mrad;
D:S
theoretical (= 1/ IFOV theoretical ) = 220:1
D:S
measure
= D:S
theoretical
/3= 74:1
D:S measure ( = 1/ IFOV measure ) is the spot size needed to provide an
accurate temperature measurement. Typically, D:S measure is 2 to 3 times
smaller than D:S theoretical , which means the temperature measurement
area of the target need to be 2 to 3 times larger than that determined by the
calculated theoretical D:S.
Focal Length
7.5mm
Horizontal FOV Vertical FOVIFOV
21° 21° 4.53mrad
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