After having developed laser polishing, the Fraunhofer Institute for Laser Technology ILT in Aachen has now also developed an ablative process for the ultra-precise machining of optics. Laser Beam Figuring (LBF) enables an ablation of less than 5 nm. For the first time, a complete process chain for the laser-based optics production has been made possible.
Thanks to their good imaging properties, aspheres are the dream of many optical designers. Aspheres have one great disadvantage, however: mechanical processing, which is much more time-consuming than for conventional spherical optics. And for a high surface quality, a special post-treatment is often necessary.
The LBF process is particularly suitable for the correction of non-spherical optics in small to medium quantities.
© Fraunhofer ILT, Aachen, Germany.
Laser polishing is a first step towards simplifying this surface finishing issue. In laser polishing, the glass surface is heated with CO2 laser radiation to just below the evaporation temperature. The viscosity of the surface sinks, the roughness flows out and the surface is smoothed.
This way, the micro-roughness can be improved quickly.
For periodic structures with a wavelength of more than 100 μm, which can occur during mechanical processing, laser polishing is not enough. This requires ultra-precise ablation processes.
Laser Beam Figuring
For ultra-precision machining with a few nanometers’ removal, Ion Beam Figuring (IBF) and Magnetorheological Finishing (MRF) have been the methods of choice. The experts at Fraunhofer ILT have now developed a laser-based method that can work more accurately and faster.
In Laser Beam Figuring (LBF), a pulsed CO2 laser removes glass material from the surface. The ablation rate can be precisely controlled by regulating the pulse duration. The lateral resolution of the ablation is essentially determined by the size of the laser spot. For example, a vertical resolution of less than 5 nm and a lateral resolution of less than 100 μm are possible during ablation.
Unlike the IBF, the LBF process does not require a vacuum; nor does it need any additional fluids, unlike MRF. At the same time, LBF enables maximum flexibility in shaping, as the non-contact process works on surfaces of almost any shape.
First Continuous Laser-based Process Chain in Optics Production
With LBF, Fraunhofer ILT has created the first continuous laser-based process chain in optical production. In a first step, the material is removed relatively coarsely for an individual shape. Then the surface is polished with the laser. For the final shape correction then the LBF is used.
Thanks to its speed and flexibility in surface design, the LBF process is particularly well suited for cost-effective shape correction of non-spherical optical components in small to medium quantities. In addition to aspheres, micro-optics can also be processed. The laser shape correction can be combined with both laser polishing and conventional machining methods.
The work has been funded by the Federal Ministry of Education and Research (BMBF), among others, as part of the RapidOptics project under grant number 13N13294.
Fraunhofer ILT will be presenting the LBF process and other laser-based technologies for optical production from May 15 to 17 at Optatec in Frankfurt. You will find the Fraunhofer Joint Stand F14 in Hall 3.0.
Christian Weingarten M. Sc.
Telephone +49 241 8906-282
Dr.-Ing. Edgar Willenborg
Group Manager Polishing
Telephone +49 241 8906-213
Petra Nolis M.A. | Fraunhofer-Institut für Lasertechnik ILT
Gamma-ray flashes from plasma filaments
18.04.2018 | Max-Planck-Institut für Kernphysik
How does a molecule vibrate when you “touch” it?
17.04.2018 | Universität Regensburg
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
In an article that appears in the journal “Review of Modern Physics”, researchers at the Laboratory for Attosecond Physics (LAP) assess the current state of the field of ultrafast physics and consider its implications for future technologies.
Physicists can now control light in both time and space with hitherto unimagined precision. This is particularly true for the ability to generate ultrashort...
The Atlantic overturning – one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards – is weaker today than any time before in more than 1000 years. Sea surface temperature data analysis provides new evidence that this major ocean circulation has slowed down by roughly 15 percent since the middle of the 20th century, according to a study published in the highly renowned journal Nature by an international team of scientists. Human-made climate change is a prime suspect for these worrying observations.
“We detected a specific pattern of ocean cooling south of Greenland and unusual warming off the US coast – which is highly characteristic for a slowdown of the...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
18.04.2018 | Materials Sciences
18.04.2018 | Materials Sciences
18.04.2018 | Materials Sciences