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7 Optical specifications
·
Immersion depth for lenses
·
Position accuracy of the sensor
7.1 Immersion depth for lenses
Some C-mount lenses reach deep into the camera flange. This may cause the lens to push against the back
of the filter glass inside the camera or even make it impossible to screw in the lens.
The table below indicates the maximum possible immersion depth. The actual immersion depth of a lens is
given in the relevant data sheet. As lens parts with a small diameter are allowed to reach deeper into the
camera flange, the immersion depths are specified based on the diameter (named as A, B, and C in the
image below).
Beside the immersion depth also the back focal length has to be considered, that means the distance between
the last lens and the sensor (named "bfl" in the image below). The back focal length can be calculated for C-
mount with the following formula:
bfl
17.526
x
x stands for the maximum immersion depth (see table below).
Fig. 2: Camera front (sectional view)
The data given in the table include the following tolerances as a safety clearance:
·
Immersion depth: 0.2 mm
·
Diameter: 0.2 mm
Type
Thread depth
(min.)
C-mount 5 mm
January 2020
for diameter at lens end
[mm]
Ø A
24.0
Technical Manual: GigE uEye FA
resulting maximum
immersion depth [mm]
11.0
minimum required back
focal length [mm]
6.5
12
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