The edge intensity [in %] of a line scan signal is determined by the illumination and the field angle w. Even for homogeneous illumination, the signal amplitude decreases towards the ends of the line
In these examples, the edge intensities are 90% and 73% of the center intensity, respectively.
Edge intensities calculated for two different fieldangles using the same sensor length S = 28.7 and magnification β = 0.25:
a) Focal length f = 50 mm
Field angle w = 13°
Edge intensity = 90%
b) Focal length f = 28 mm
Field angle w = 22.3°
Edge intensity = 73%
Schematic depiction of the imaging system and definition of variables used.
f = Lens focal length (mm)
S = Sensor length (mm)
L = Length of Region of Interest (ROI) of object (mm)
a = Object range (mm)
a’ = Image distance: Distance from sensor to HH’ (mm)
β = Magnification
w = Field angle
OO’ = Distance from sensor to measured zone (mm)
s’A = Flange focal length (mm)
∆s’ = Lens extension (mm)
LT = Tube length
A = Working distance (mm)
HH’ = Principal point distance (mm) (can lengthen or shorten OO’)
s’K = Camera flange length consisting of focus adapter series FA22 and extension rings series ZR (mm)
LO = Lens length (mm)
