Functional description
Chapter 4
MN051_v1.0.5
2-Axis Laser Beam Deflection Units
13
Only for deflection units fitted with an F-Theta lens
4.2
F-Theta lens
The F-Theta lens is specially designed for use with 2-axis deflection units. It focuses the laser
beam at optimum quality on any position in the marking field. At the same time, it provides
partial optical compensation for the barrel-shaped distortion that is unavoidable when using a
two-axis deflection unit. The remaining distortion (see below) must be compensated by the
deflection unit drive.
Distortion caused by two-mirror
deflection.
Distortion caused by F-Theta
lens.
Distortion caused by two-
mirror deflection. and F-Theta
lens.
1 Lens element inc. lens
2 Glass guard
3 Clamp ring
4 Protective cap
Assembly instructions
o
Before installation, check the protection window for dirt, scratches or cracks.
-
If the protection window is dirty, it must be cleaned (
page 19, Instructions for
cleaning lenses and glass guards).
-
If the protection window is scratched or cracked, it must be replaced.
o
Brush the outer thread of the protective glass with a small amount of special grease for
photo-mechanical components. Normal fats are not suitable because they release gases
and thus the optical system can be destroyed.
o
Screw the protection window and mount into the beam output on the deflection unit until it
is positioned securely.
Fig. 3
Field distortion
with and without
F-Theta lens
Fig. 4
Example: F-
Theta lens for
Nd:YAG
