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SPIE Optical Systems Design: freeform lens shrinks desktop laser cutters

15 Sep 2021

Novel beam shaper developed at Vrije University Brussels also enables deeper cuts with compact diode laser systems.

A team at Vrije University in Brussels, Belgium, has teamed up with commercial desktop laser cutter provider “Mr Beam” to develop a new freeform lens that improves performance while shrinking the size of the overall system.

Describing the work in a presentation at this week’s SPIE Optical Systems Design Digital Forum, Lien Smeesters highlighted how industrial laser cutting systems based around carbon dioxide lasers offered excellent beam quality but required extremely large and expensive optical designs.

“We are interested in the miniaturization of this technology towards compact desktop laser cutters, laser cutters that can be integrated in your office, at your home, and can be of interest for hobbyists and architects - which use laser diodes instead,” she explained.

“We targeted the development of a single optical component enabling [us] to transform the divergence of the beam of the laser diodes to a circular, focused spot featuring a large depth of focus optimized for laser cutting applications.”

At the moment, that is typically achieved with a combination of spherical and cylindrical lenses. However, this means a bulky optical design.

“We want to combine the functionality of the cylindrical lenses and the aspherical two lenses into one freeform component,” Smeesters said.

Deeper cuts
After conducting simulations on a system based around a 450 nm diode laser emitting 5 W power - sufficient for small-scale cutting of materials including fabrics, cardboard, and paper - Smeesters and colleagues designed a lens with one spherical side and a second, aspherical surface.

“[The] rear side of the lens is a biconic aspherical surface,” she said, adding that the component produced a beam diameter of approximately 19 µm with “almost perfect” circular spots. A biconic lens has two different radii on a single surface.

The depth of focus with the new optical component was also increased to 4.8 mm, beyond both the targeted 4 mm and the prior figure of 2 mm with conventional optics - meaning that thicker materials could now be cut.

However, the asymmetric nature of the novel freeform component means that the circularity of the beam changes dramatically with rotation, meaning that an alignment tool was needed in the proof-of-concept demonstrator system developed with Mr Beam.

“Using our novel optics, we can see that we have a circular beam, which will improve the cutting resolution and also give an equal cutting resolution in the x and in the y-direction, which is favorable for the cutting quality,” concluded Smeesters.

“In addition, by decreasing the spot size, we are able to increase the cutting resolution and the cutting speed - since we have higher irradiance - but also enable an extended range of cuttable materials.”

Showing off the additional capability with a video of the new laser cutter from Mr Beam, the Vrije University researcher said that the design paved the way towards further miniaturization of desktop laser cutters, while offering improved cutting performance.

• The SPIE Optical Systems Design Digital Forum is taking place this week, in tandem with SPIE's Security+Defence and Remote Sensing virtual conferences.

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