Inspired by an ancient light trick, technology could enable a new type of 3D display —


For the primary time, researchers have used liquid crystals to create a flat magic window — a clear gadget that produces a hidden picture when gentle shines on it. The expertise represents a brand new twist on a really outdated gentle trick.

Hundreds of years in the past, artisans in China and Japan made bronze mirrors that seemed like a standard flat mirror whereas viewing one’s reflection however fashioned one other picture when hit by direct daylight. It took till the early twentieth century for scientists to grasp that these gadgets work as a result of a picture solid into the again of the mirror creates small floor variations that trigger the picture to kind — and it took till now for engineers to use the identical precept to liquid crystals for high-tech shows.

“The magic window we created seems completely flat to the bare eye however, actually, has slight variations that create a picture in response to gentle,” mentioned analysis crew chief Felix Hufnagel from the College of Ottawa. “By designing the window to be comparatively easy, the picture that’s created may be seen over a wide variety of distances from the window.”

In Optica, Hufnagel and colleagues describe the method they developed for creating clear liquid crystal magic home windows that may produce any desired picture. The method can be used to create magic mirrors that mirror, moderately than transmit, gentle to create a picture.

“Utilizing liquid crystals to make magic home windows or mirrors may someday make it attainable to create a reconfigurable model for producing dynamic creative magic home windows or films,” mentioned Hufnagel. “The power to acquire a protracted depth of focus may additionally make the method helpful for 3D shows that produce steady 3D pictures even when seen from completely different distances.”

Creating magic with liquid crystals

Though scientists have understood for many years that the traditional bronze magic mirrors fashioned pictures on account of small floor variations, it was not till 2005 that Michael Berry, a mathematical physicist on the College of Bristol within the UK, derived the mathematical foundation for this impact. He later prolonged this data to develop a theoretical foundation for clear magic home windows along with reflective magic mirrors. This work impressed Hufnagel and colleagues to create a magic window based mostly on liquid crystals.

Liquid crystals are supplies that may circulate like a traditional liquid however have molecules that may be oriented like a stable crystal. Within the new work, the researchers used a modified model of a widely known fabrication course of that produces a particular liquid crystal sample that enables a desired picture to be created when illuminated.

They used a Pancharatnam-Berry Optical Aspect (PBOE), which is a liquid crystal gadget that operates beneath a widely known precept referred to as the Pancharatnam-Berry section. By altering the orientation of liquid crystal molecules on this gadget, the researchers may alter the properties of the sunshine because it travels by means of the gadget on a pixel-by-pixel foundation.

Steady pictures over a number of distances

“On a conceptual stage, the idea developed by Berry was instrumental in figuring out how these liquid crystals have to be oriented to create a picture that’s steady over a big distance,” mentioned Hufnagel. “Our use of flat optical components and a liquid crystal sample with light variations prescribed by Berry’s Laplacian picture idea permits the magic home windows to look regular, or flat, when one appears to be like by means of them.”

After fabricating a magic mirror and window, the researchers used a digital camera to measure the sunshine depth patterns produced by each gadgets. When illuminated with a laser beam, each the mirror and window produced a visual picture that remained steady at the same time as the gap between the digital camera and the mirror or window modified. The researchers additionally confirmed that the gadgets created pictures when illuminated with an LED gentle supply, which might be extra sensible to make use of in real-life functions.

The researchers are actually working to make use of their fabrication method to create quantum magic plates. For instance, two of those plates may create entangled pictures which one may use to check new quantum imaging protocols. They’re additionally exploring the opportunity of fabricating magic home windows utilizing approaches apart from liquid crystals. For example, utilizing dielectric metasurfaces to make a magic window gadget may cut back its footprint whereas growing bandwidth.

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