Back Focal Variance When Using Any Filter - Teledyne m640 User Manual

The graphic below shows a sample response of a color camera with an overlay of the cut-off filter
suppressing wavelengths above 650nm from reaching the camera sensor.

Back Focal Variance when using any Filter

Inserting a filter between a lens and sensor changes the back focal point of the lens used. A
variable focus lens simply needs to be adjusted, but in the case of a fixed focus lens, the changed
focal point needs correction.
The following simplified illustration describes this but omits any discussion of the Optics, Physics,
and the math behind the refraction of light through glass filter media.
Additional Reference Information • 215
Nano Series GigE Vision Camera