MD 9930 Thermal camera
Operation details
11
5. Operation details
Lens and camera field of view
This table lists the horizontal Filed of view (FOV), vertical FOV and IFOV for lens.
Focal Length
Horizontal FOV
Vertical FOV
IFOV
9 mm
19°
25°
2.78 mrad
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
theoretical
is distance to a measured object caught in a single pixel. It is the
distance at which the given object’s temperature can be theoretically measured. At
unity distance, the IFOV can be then directly translated to the object’s size.
For accurate temperature measurement, the spot has to be about three times the
size of than at DTS
theoretical
, or the distance to it must be 3 times shorter.
𝐼𝐹𝑂𝑉 =
𝑃𝑖𝑥𝑒𝑙 𝑠𝑖𝑧𝑒
𝐿𝑒𝑛𝑠 𝑓𝑜𝑐𝑎𝑙 𝑙𝑒𝑛𝑔𝑡ℎ
𝐷𝑇𝑆
𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙
=
1
𝐼𝐹𝑂𝑉
𝐷𝑇𝑆
𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑
=
𝐷𝑇𝑆
3
EXAMPLE:
The FOV of the camera is 21° x 21°, which is about 0.36 x 0.36 rad. The detector
resolution for this example is 80 x 80 pixel. Each pixel then covers about 4.53 mrad,
which is IFOV. This means that at 1 m distance, each pixel is covering 4.53 mm
2
actual space. Temperature can be accurately measured on about 13.6 mm
2
at 1m
distance. If turned the other way, DTS can be the calculated distance at which each
pixel will cover 1 m
2
space, which is about 220 m. Thermal camera uses for example
7.5 mm lens, so knowing the IFOV gives the pixel size of the detector as 34 μm
2
.
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.
220m
19°
25°
120m
120m
Spot size 1m x 1m
