The Fiber Laser Optical Train
Inside an industrial fiber laser cutting head, laser energy leaves the delivery fiber core (typically 50μm or 100μm) as a highly divergent cone of monochromatic light at 1064nm.
To focus this energy into a high-density piercing spot capable of vaporizing steel, the optical train requires two distinct lens assemblies: the collimator and the focuser.
The Collimating Lens: Divergence to Parallel Beam
The collimating lens group is positioned immediately below the QBH/QD fiber connector. Its function is to catch the expanding laser beam cone and convert it into a parallel, non-diverging column of light.
Common collimator focal lengths include F75mm, F100mm, and F125mm. Changing collimator focal length alters the beam magnification ratio.
The Focusing Lens: Concentrating Energy Density
The focusing lens group takes the parallel laser column and refracts it down to a micro-spot (0.1mm to 0.3mm diameter) on the sheet metal surface.
Focus focal lengths (F125mm, F150mm, F200mm) determine focal depth and spot size: shorter focal lengths create intense spot density for thin sheet speed, while longer focal lengths provide greater depth of focus for thick plate piercing.
Achromatic Doublet Pairs & Cleanroom Assembly
High-power fiber laser lenses are manufactured as cemented or air-spaced doublet pairs to eliminate spherical aberration. Never disassemble optical doublets outside an ISO Class 7 cleanroom bench.
Frequently Asked Questions
Why do focus and collimating lenses fail in laser machines?↓
90% of failures stem from dirty assist gas or lower protective window burnout that allows heat and piercing spatter into the internal barrel.
Have questions regarding optical tolerances or maintenance?
Connect directly with TriQuench India Director desk at Rakhial, Ahmedabad.