An inexpensive and fast method of making free-form optics can benefit applications from glasses to telescopes
Image: The researchers used their new method to manufacture optical elements with various geometric shapes—including toroids and trilobes—up to 200 mm in size and free-form surfaces. The surface quality of the lens is similar to the best polishing technique available, and it is orders of magnitude faster and simpler to make. see more
Image source: Technion-Israel Institute of Technology
Washington - Researchers have developed a method to make free-form optical elements by shaping a certain volume of curable liquid polymer. This new method is expected to produce prototypes of custom optical components faster for a variety of applications, including corrective lenses, augmented and virtual reality, self-driving cars, medical imaging, and astronomy.
Common devices such as glasses or cameras rely on lenses—optical elements that have spherical or cylindrical surfaces or slightly deviate from these shapes. However, more advanced optical functions can be obtained from surfaces with complex topography. At present, it is very difficult and expensive to manufacture such free-form optical devices due to the special equipment required for machining and polishing the surface.
"Our method of making free-form surfaces can achieve extremely smooth surfaces, and can be achieved using basic equipment that can be found in most laboratories," said Moran Bercovici, research team leader from Technion at the Technion-Israel Institute of Technology. "This makes the technology very easy to use, even in resource-poor environments."
In Optica, the high-impact research journal Optica of the Optica Publishing Group, Bercovici and colleagues show that their new technology can be used to produce free-form components with sub-nanometer surface roughness in just a few minutes. Unlike other prototyping methods such as 3D printing, even if the volume of the manufactured parts increases, the manufacturing time is still very short.
“Currently, optical engineers pay tens of thousands of dollars for specially designed free-form surface components, and then wait for several months to arrive,” said Omer Luria, one of the authors of the paper. "Our technology is expected to fundamentally reduce the waiting time and cost of complex optical prototypes, which can greatly accelerate the development of new optical designs."
From glasses to complex optics, researchers have decided to develop this new method after learning that 2.5 billion people worldwide do not have access to corrective glasses. "We set out to find a simple way to manufacture high-quality optical components that does not rely on machining or complex and expensive infrastructure," said Valeri Frumkin, who first developed the method in Bercovici's laboratory. "Then we discovered that we can extend our method to produce more complex and interesting optical terrain."
One of the main challenges in manufacturing optical devices by curing liquid polymers is that for optical devices larger than about 2 mm, gravity dominates the surface forces, which causes the liquid to flatten into puddles. To overcome this problem, researchers have developed a method of manufacturing lenses using liquid polymer immersed in another liquid. Buoyancy counteracts gravity and makes surface tension dominate.
Since gravity is not in the picture, researchers can create a smooth optical surface by controlling the surface morphology of the lens liquid. This requires the lens liquid to be injected into the support frame so that the lens liquid wets the inside of the frame and then relaxes into a stable structure. Once the desired shape is achieved, the lens liquid can be cured by ultraviolet radiation or other methods to complete the manufacturing process.
After using liquid manufacturing methods to create simple spherical lenses, the researchers expanded to optical elements with a variety of geometric shapes-including rings and trilobes-up to 200 mm in size. They showed that the resulting lenses exhibited surface quality similar to the best polishing techniques available, while being produced at a speed and production that was orders of magnitude simpler. In the work published on Optica, they further expanded the method of creating free-form surfaces by modifying the shape of the support frame.
Infinite Possibilities "We have identified infinitely possible optical terrains that can be made using our method," said Mor Elgarisi, the lead author of the paper. "This method can be used to manufacture components of any size, and since the surface of the liquid is naturally smooth, there is no need for polishing. This method is also applicable to any liquid that can be solidified, and has the advantage of not generating any waste."
Researchers are now working to automate the manufacturing process so that various optical topography can be made in a precise and repeatable manner. They are also experimenting with various optical polymers to find out which can produce the best optical components.
Paper: M. Elgarisi, V. Frumkin, O. Luria, M. Bercovici, "Making free-form optical elements through fluid forming", Optica, 8, 11, 1501-1506 (2021). DOI: 10.1364/OPTICA.438763.
Optica is an open access journal dedicated to the rapid dissemination of high-impact peer-reviewed research across the entire optics and photonics field. The magazine is published monthly by Optica Publishing Group and provides a forum for the international community to quickly access groundbreaking research, whether it is theoretical research or experimental research, basic research or applied research. Optica has an outstanding editorial board composed of more than 60 associate editors from all over the world, and is supervised by the editor-in-chief Prem Kumar of Northwestern University. For more information, please visit Optica.
About Optica Publishing Group (formerly OSA)
Optica Publishing Group is a division of Optica, which is a society that promotes the development of global optics and photonics. It publishes the largest collection of peer-reviewed content in the field of optics and photonics, including 18 prestigious journals, the society's flagship member magazine, and papers from more than 835 conferences, including more than 6,500 related videos. Optica Publishing Group has more than 400,000 journal articles, conference papers and videos available for search, discovery and access, representing a full range of research in this field around the world.
Aaron Cohen (301) 633-6773 aaroncohenpr@gmail.com mediarelations@optica.org
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Manufacturing free-form optical components through fluid forming
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Moran Bercovici Technion – Technion-Israel Institute of Technology mberco@technion.ac.il
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Copyright © 2021 American Association for the Advancement of Science (AAAS)