Lasers and bubbles combine to create 3D images in liquid

Lasers and bubbles combine to create 3D images in liquid
Researchers from Utsunomiya University in Japan have developed a volumetric 3D display which uses lasers to create bubbles inside a liquid screen. This allows viewers to see a 3D image in the columnar display from all angles without any 3D glasses or headsets.

The research, first published in Optica, the Optical Society's journal, demonstrated the ability of the volumetric bubble display to create changeable colour graphics.

"Creating a full-color updatable volumetric display is challenging because many three-dimensional pixels, or voxels, with different colors have to be formed to make volumetric graphics," said Kota Kumagai, first author of the paper. "In our display, the microbubble voxels are three-dimensionally generated in a liquid using focused femtosecond laser pulses. The bubble graphics can be colored by changing the color of the illumination light."

This technology is still in the prototype stage but possible applications include visitor attractions, where viewers could walk around the display. It could also be used in military and healthcare sectors, to help doctors visualise a patient's body prior to surgery or let the military study terrain and buildings prior to a mission.

"The volumetric bubble display is most suited for public facilities such as a museum or an aquarium because, currently, the system setup is big and expensive," said Kumagai. "However, in the future, we hope to improve the size and cost of the laser source and optical devices to create a smaller system that might be affordable for personal use."

The team uses lasers that shoot femtosecond (one quadrillionth of a second) pulses of light into precise locations within a viscous liquid. As the liquid absorbs multiple photons at the points where those pulses are focused, small bubbles form. Because the liquid is fairly thick, those bubbles stay in place instead of floating to the top right away. Each one of them constitutes a 3D pixel (called a voxel) of the complete holographic image.

In order for that image to be seen easily, the liquid has to be exposed to an external light source such as an LED. The bubbles catch and scatter that light, causing the image to visually 'pop out' from the surrounding liquid.

At the moment the system is driven by one colour, but the team believes projectors could be used to focus different colours onto different parts of the image simultaneously.

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