389Appendices
© 2010 Thorlabs
10.1.1.3
Flange Back Distance
10.1.1.3.1 Calculation of the flange back distance
To correctly determine the flange back distance of a DCx camera, you need to consider the distance
between the lens flange and the active area of the sensor and, additionally, the type and thickness of
any materials inserted into the optical path.
The distance in air between the threaded flange and the active area is 17.526 mm with C-mount
lenses and 12.526 mm with CS-mount lenses.
This mechanical distance can change due to the material-specific refractive index of the inserted
materials. The glass cover of the sensor and all filters inserted into the optical path must be taken
into account in the calculation.
Figure 86 Calculation flange back distance (schematic demonstration)
x = Distance screwed flange PCB (flange back distance)
a = Distance screwed flange active sensor area (17,526mm)
e = Distance active sensor area PCB
d = Thickness of the glass cover of the sensor
f = Thickness of the filter (optional)
n = Refractive index
h = Maximum sensor height over the PCB
You can use the following formula to calculate the mechanical flange back distance:
Table 17: Parameters for calculating the flange back distance for DCx cameras
x (with filter
glass) [mm]