Holograms shrink projection tech

Projection technology is set to get smaller and cheaper thanks to what is being described as a "holographic projection system with lensless zoom function". The unit has been developed by university researchers in Japan and Poland in an effort to make miniature projection devices that can be easily integrated into a variety of electronic devices.

Researchers from Chiba University in Japan and the Warsaw University of Technology published their findings in a paper titled ‘Lensless zoomable holographic projection using scaled Fresnel diffraction’ in Optics Express, the journal of the Optical Society (OSA).

The teams - led by Chiba’s Tomoyoshi Shimobaba and Michal Makowski, Warsaw University of Technology – claim the technology development is unique because it only requires a laser and an LCD panel and no lenses or mechanical components.

"A zoom lens in general projectors occupies a large area in the systems," said Shimobaba, a professor in the graduate school of engineering at Chiba University in Japan. "If I remove the zoom lens, the system will be small and cost-saving."

The lensless zoom was achieved using holography techniques. The OSA says "[Holography is a way to produce images by using the interference pattern of two laser beams to encode and later display the image. By their nature holograms operate without lenses. It is possible to represent a holographic image with numbers and formulas and then calculate how that image can be magnified."

Shimobaba and his team made modifications to the standard magnification formulas to reduce calculation time and preserve image quality. Magnified holograms can suffer from a signal processing effect called aliasing, which can result in visual distortions of the original image. The researchers developed a calculation to reduce aliasing effects and also used a method developed by another team of researchers to reduce the speckle noise effect that can give holograms a grainy appearance. They tested the technique by increasing by nine times the size of a monochrome picture of a woman in a feathered hat.

Currently the footprint of the holographic zoom system is about 160x80x40 millimeters, and Shimobaba believes the researchers can easily shrink it even further. "Currently we use commercial parts," he said. "However, if we customise the components we believe we can develop the smallest projector [to date] because our technique is in principle the simplest." He estimates that the technology could be commercialised in the next five to ten years.

Going forward the researchers plan to refine their mathematical image manipulation techniques to further improve image quality and reduce calculation time. They also plan to test the technique with colour images.