Functional description
Chapter 4
Only for deflection units fitted with an F-Theta lens
4.2
F-Theta lens
The F-Theta lens is designed especially for use with 2-axis deflection units. It focuses the
laser beam at optimum quality to any position on the marking field. At the same time, it pro-
vides 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 Protective glass
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 20, Instructions for
cleaning lenses and protective glasses).
-
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 of 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
MN065_v1.0.1
2-Axis Laser Beam Deflection Unit SS-II
15
