SZL25 Zoom Lens Assembly
The SZL25 zoom lens is designed for CO2 laser beams of up to 1000W power, depending upon the input beam
diameter. It has a clear input diameter of 25mm and a zoom focal length range of 50mm to 150mm at a fixed
focal plane. The 3:1 range of focal length results in a 9:1 range of energy density and depth-of-focus for a given
During the zoom action, which is manually controlled by the laser operator, the system will not generally need
a change of z-axis setting or a change of gas nozzle.
Model SZL25 has a mechanical fitting exactly equivalent to standard 1.1″ diameter mounted lenses, such as
the 11ZLF and 11TF types.
Dimensions : see Figure 24.511.
Zoom range : 49.4mm to 152.3mm.
Engraved range : 50.0mm to 150.0mm.
Beam compression ratio : 1.7 to 1.
Input fitting : 1.5″ x 12TPI UNF 2A.
Output fitting : 1.875″ x 20TPI UNF.
Input aperture : 25.0mm diameter.
Max gas pressure : 200psi., safety factor > 2.
Centration : < 5 arc min (see section 24.00).
Cooling : Air, or indirect water cooling via WMA (see section 20.3).
Construction : 3 ZnSe lens elements in black-anodised aluminium housing.
Model SZL25 zoom lens is a direct fit to FF25 (section 63.1) and CFF25 (section 63.2) manual focus units, either
directly or via the WMA water-cooling mount accessory.
The 1.5″ x 12TPI mounting thread is identical to that of the standard M11 cell used for 11MZLF, 11HGP and 11TF
lenses (sections 8.10, 20.1), and so this zoom lens may be retro-fitted to equipment designed for those lens types.
At the output of the lens the thread fitting is designed to accept either of two gas nozzles:
Model GNA50 for up to 90psi (section 20.6), or,
Model SNA50 for up to 200psi (section 9.10).
(NB: GNA nozzles have an external control ring for speedy setting of nozzle stand-off. See applications notes
Zoom lenses may be used to help determine the ideal cutting or processing parameters for a range of materials
and material thicknesses. A change of material or material thickness may require, for best results, a change of
assist gas type or pressure. If gas conditions are changed then the nozzle stand-off may also require minor
In applications where assist gas is used, (such as cutting), the gas flow conditions will almost always need
modifying to suit the changes in optical setting if the laser operator seeks optimum process speed.
For high power lasers, in excess of 1kW CW power, see for example ‘GPZ25’ zoom lens, section 24.53.