METREL MD 9930 Benutzerhandbuch Seite 12

METREL MD 9930
Focal Length
9 mm
IFOV (Instantaneous Field of View) is the size of the object caught in the single pixel
on the detector. It is given as spatial angle with unit mrad. It depends on the lens and
detector size.
DTS is distance to spot. It is the distance at which the given size spot can be
theoretical
measured. At unity distance, the IFOV can be then directly translated to spot size.
For accurate temperature measurement, the spot has to be about three times the
size of DTS
theoretical
EXAMPLE:
The FOV of the camera is 21° x 21°, which is about 0.36x 0.36 rad. The detector
resolution is 80x80 pixel. Each pixel then covers about 4.53 mrad, which is IFOV.
This means that at 1m distance, each pixel is covering 4.53mm
Temperature can be accurately measured on about 13.6mm
turned the other way, DTS can be the calculated distance at which each pixel will
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cover 1m space, which is about 220m. Thermal camera uses 7,5mm lens, so
knowing the IFOV gives the pixel size of the detector as 34um.
120m
120m
Focus
To adjust focus rotate the IR lens clockwise or anti-clockwise. When target comes
into focus, it shows a sharp image. When the target moves out of focus, the thermal
image becomes blurry.
NOTE
Correct focus is important in all imaging applications. Correct focus makes sure that
the infrared energy is correctly directed onto the pixels of the detector. Without the
correct focus, the thermal image can be blurry and the radiometric data will be
inaccurate. Out-of-focus infrared images are of little value.
Horizontal FOV
19°
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Spot size 1m x 1m
19°
25°
220m
Vertical FOV
25°
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Operation
IFOV
2.78mrad
2
actual space.
2
at 1m distance. If