Laser-generated bubbles create 3D images in liquid display

Scientists have developed a new technology that creates 3D images by using a laser to form tiny bubbles inside a liquid screen, allowing users to view images in a columnar display from all angles without any special glasses or headsets.
Instead of rendering a 3D scene on a flat surface, the display itself is three-dimensional, a property known as volumetric.
This allows viewers to see a 3D image in the columnar display from all angles without any 3D glasses or headsets.
"Creating a full-colour updatable volumetric display is challenging because many three-dimensional pixels, or voxels, with different colours have to be formed to make volumetric graphics," said Kota Kumagai, from Utsunomiya University in Japan.

"The microbubble voxels are three-dimensionally generated in a liquid using focused femtosecond laser pulses. The bubble graphics can be coloured by changing the colour of the illumination light," said Kumagai.
The technology might one day allow full-colour updatable volumetric displays, which may be used for art or museum exhibits, where viewers can walk all around the it.

They are also being explored for helping doctors visualise a patient's anatomy prior to surgery or to 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.

"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," he said.
The bubbles for the new display are created by a phenomenon known as multiphoton absorption, which occurs when multiple photons from a femtosecond laser are absorbed at the point where the light is focused.
Multiphoton absorption allowed the researchers to create microbubbles at very precise locations by moving the focus of the laser light to various parts of a liquid-filled cuvette that acted as a "screen."
Using a thick, liquid prevents the bubbles, once formed, from immediately rising to the top of the liquid.

The bubble graphics are viewable when they scatter light from an external light source such as a halogen lamp or high-power LED.
The researchers produced monochromatic images in white, red, blue and green by switching the colour of the LED.
Illuminating the graphics with a projector could create different colours in different regions of the image.
Rather than creating each bubble one by one, the researchers used a computer-generated hologram to form 3D patterns of laser light that let them control the number and shapes of the microbubble voxels.
Researchers demonstrate their technique by creating a sequence of 2D bubble images of a mermaid, a 3D rendered bunny, and 2D dolphin graphics in four different colours.

The study was published in the journal Optica.