Researchers have developed a spiral-shaped lens that maintains clear focus at different distances in different light conditions. The new lens works very similar to progressive lenses used for vision correction, but without the distortions normally seen with such lenses. It could help advance technologies for contact lenses, intraocular cataract implants and miniaturized imaging systems.
“Unlike existing multifocal lenses, our lens performs well in a wide range of light conditions and maintains multifocality regardless of pupil size,” said Bertrand Simon of the Laboratory of Photonics, Numerics and Nanosciences (LP2N), a unit joint research project between the Institut d’Optique Graduate School, the University of Bordeaux and the CNRS of France. “For potential implant users or people with age-related farsightedness, it could provide clear and constant vision, potentially revolutionizing ophthalmology.”
In OPTICAL, the high-impact research journal from Optica Publishing Group, the researchers describe the new lens, which they call a spiral diopter. Its spiral functions are arranged in a way that creates many separate focus points, much like having multiple lenses in one. This makes it possible to see clearly at various distances.
“In addition to ophthalmic applications, the simple design of this lens could greatly benefit compact imaging systems,” Simon said. “It would simplify the design and operation of these systems while providing a way to achieve imaging at various depths without additional optical elements. “These capabilities, along with the multifocal properties of the lens, offer a powerful tool for depth perception in advanced imaging applications.”
Creating a vortex of light
The inspiration for the spiral lens design came when the paper’s first author, Laurent Galinier of SPIRAL SAS in France, was analyzing the optical properties of severe corneal deformations in patients. This led him to conceptualize a lens with a unique spiral design that causes light to spin, like water going down a drain. This phenomenon, known as optical vortex, creates multiple clear focus points, allowing the lens to provide clear focus at different distances.
“Creating an optical vortex typically requires multiple optical components,” Galinier said. “Our lens, however, incorporates the elements necessary to form an optical vortex directly on its surface. “Creating optical vortices is a thriving field of research, but our method simplifies the process, marking a significant advance in the field of optics.”
The researchers created the lens by using advanced digital machining to mold the unique spiral design with high precision. They then validated the lens by using it to generate images of a digital ‘E’, much like those used on an optometrist’s illuminated board. The authors observed that image quality remained satisfactory regardless of the aperture size used. They also discovered that the optical vortices could be modified by adjusting the topological loading, which is essentially the number of windings around the optical axis. Volunteers who wore the lenses also reported notable improvements in visual acuity at a variety of distances and lighting conditions.
Making the new lens a reality required combining intuitively crafted design with advanced manufacturing techniques through interdisciplinary collaboration. “The spiral diopter lens, first conceived by an intuitive inventor, was scientifically substantiated through intense research collaboration with optical scientists,” Simon said. “The result was an innovative approach to creating advanced lenses.”
The researchers are now working to better understand the unique optical vortices produced by their lens. They also plan to conduct systematic testing of the lens’s ability to correct vision in people to comprehensively establish its performance and advantages in real-world conditions. Additionally, they are exploring the possibility of applying the concept to prescription glasses, which could offer users clear vision at multiple distances.
“This new lens could significantly improve people’s depth of vision in changing lighting conditions,” Simon said. “Future developments in this technology could also lead to advances in compact imaging technologies, wearable devices and remote sensing systems for drones or autonomous vehicles, which could make them more reliable and efficient.”
L. Galinier, P. Renaud-Goud, J. Brusau, L. Kergadallan, J. Augereau, B. Simon, “Spiral diopters: free-form lenses with improved multifocal behavior”, 11, 2 (2023).
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