Artificial sheet materials could expand the capabilities of holography Holographic displays offer the ultimate 3D viewing experience by creating lifelike images but are limited by current technology’s narrow viewing angles and small image sizes. A new method that uses wavefront shaping could tackle these limitations. Industrial Technologies © immimagery/stock/adobe.com Holographic displays are at the forefront of 3D visualisation technology, capable of creating highly realistic scenes with full motion parallax. This apparent shift of the holographic image in a way that mimics how objects in the real world would appear from different angles makes them appear as though they are truly existing in three dimensions. Holographic technology holds significant promise for a wide range of applications, including augmented and virtual reality, medical imaging, interactive displays and 3D mapping. However, this field encounters a fundamental research hurdle. Holograms contain far more detail and complexity than what today’s spatial light modulators (SLMs) can show. This limitation stems from the restricted ability of these devices to handle detailed imagery, owing to their small size and low resolution. Essentially, SLMs do not have enough room or bandwidth to accurately reproduce the intricate details found in holograms, affecting the quality of the 3D images produced. To fully harness the capabilities of holographic displays, it is necessary to create more efficient techniques that can handle the broad and detailed light patterns – the large optical extent – essential for producing realistic 3D holographic images. This improvement would make these visuals more immersive and life-like for viewers. Metasurfaces unlocking wider-angle views in holography “To develop high-quality holographic 3D video displays, three critical components are pivotal: an optical system capable of displaying wide-angle views, an SLM possessing high bandwidth and swift algorithms for generating computer holograms,” notes Luis Sanchez-Soto, coordinator of the EU-funded HoloWS project. “HoloWS has focused on developing a system that offers a broader viewing angle.” To this end, researchers have worked on a novel approach aiming to overcome the limitations posed by SLMs and achieve truly immersive 3D holographic displays. The technique employs metasurface-based wavefront control, which essentially allows for a significant expansion in the field-of-view beyond what traditional Fourier-based hologram displays offer. This limitation has been a longstanding challenge in the field of holography. Metasurface-based wavefront control is advanced optical technology that manipulates light wave properties – such as their direction, phase and amplitude – using ultra-thin, engineered surfaces. These are known as metasurfaces and are composed of tiny, artificially structured units that can alter the behaviour of passing light waves in specific ways. Paving the way for breakthroughs In the field of holographic displays, considerable progress is yet to be made before achieving truly photorealistic 3D holographic video displays. However, HoloWS’s development of a high space-bandwidth product system marks a significant milestone towards this goal. This space-bandwidth product reflects the trade-off between the size of the image that can be displayed and its resolution. Project advancement promises to unlock new possibilities for larger and wider-angle holographic displays, overcoming the current limitations of SLMs. “Our work is expected to inspire a wave of innovative research in areas such as holographic head-up displays and holographic illumination based on compressed sensing,” highlights Sanchez-Soto. “We are committed to further refining holographic rendering algorithms and expanding the scope of research to include interactive applications and larger display formats.” Keywords HoloWS, holographic displays, image, metasurface, bandwidth, wavefront control, spatial light modulators
