Proceedings Article | 12 September 2021
KEYWORDS: Semiconductor lasers, Laser cutting, Aspheric lenses, Tolerancing, Manufacturing, Lens design, High power lasers, Freeform optics, Beam shaping, Light sources and illumination
Laser cutters are currently finding their way from industrial environments to home-use applications, driving the development towards low-cost and compact systems. We therefore target the design of a single beam-shaping lens for use in laser cutting applications, enabling the miniaturization of the laser scanning head while pursuing optimal cutting performance. Particularly, we target the design of a beam shaping lens for use with a high-power 450 nm laser diode (5.0 Watt, 14° x 46° beam divergence), enabling to transform the divergent elliptical laser diode beam into a circular focused spot, while maximizing the depth-of-focus. We cover the complete development chain, starting from the characterization and modelling of the laser diode, to the optical design, optimization and tolerancing of the focusing lens, and the manufacturing and demonstration of the laser cutting system. The optimized beam-shaping lens features a circular focused spot diameter <100 μm over a depth-of-focus of 4.8 mm. In contrast to the current laser diode circularization and focusing designs, comprising a combination of cylindrical and plano-convex lenses, we only use a single aspheric biconic lens, giving rise to a more compact design. A tolerance analysis was included on both the optical and mechanical parameters, enabling to evaluate the design for manufacturing. Following, the novel beam-shaping lens was manufactured using ultraprecision diamond turning, and afterwards characterized using a coordinate measurement machine. Finally, the performance is evaluated in a proof-of-concept demonstrator, validating the circular illumination beam and improved cutting performance. We successfully demonstrated the operation of our novel beam-shaping lens, featuring the beam circularization and focusing using a single lens, optimized for use in compact laser cutting devices. This novel lens design paves the way towards a further miniaturization of desktop laser cutters, while showing an excellent laser cutting performance, including an improved cutting resolution and depth-of-focus, enabling a wider range of materials and extended material thicknesses.
