Back Flange Distance - FLIR GRASSHOPPER 3 Series Technical Reference

4.4.1

Back Flange Distance

The Back Flange Distance (BFD) is offset due to the presence of both a 1 mm infrared cutoff (IRC) filter and a 0.5
mm sensor package window. These two pieces of glass fit between the lens and the sensor image plane. The IRC
filter is installed on color cameras. In monochrome cameras, it is a transparent piece of glass. The sensor
package window is installed by the sensor manufacturer. Both components cause refraction, which requires
some offset in flange back distance to correct.
The resulting C-mount BFD is 17.99 mm.
For more information about the IRC filter, see
2/10/2017
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Figure 4.3: Example C-mount Cross Section
Infrared Cut-Off
®
Grasshopper 3 PGE Technical Reference
4 Grasshopper3 PGE Physical Interface
Filters.
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