Indistinguishable from Reality: Overcoming Key Challenges in Highly Realistic Holographic Display
8 April 2021
The end goal of any digital display technology is to achieve the level of immersion and quality required to make the content ‘indistinguishable from reality.’ While holography is considered the ultimate display technology, there are several challenges it needs to overcome to enable mainstream adoption. Last month, VividQ CEO Darran Milne was invited to present at the SPIE AR | VR | MR Digital Forum 2021, hosted by Bernard Kress, Partner Optical Architect at Microsoft HoloLens. In his talk, Darran explained how VividQ is ready to overcome key challenges to achieve highly realistic holographic display for mass consumer adoption.
Inherent properties of holographic display
Holographic display is the process of directly engineering light to project three-dimensional virtual objects and scenes that possess a natural depth of field. The intrinsic qualities of computer-generated holography mean that it is one of the best technologies to match up to the consumer’s expectations for achieving highly realistic holographic images:
- AR experiences with real depth: Accurate world-locked content for a far more realistic and immersive experience.
- Long-term viewing comfort: Eliminates physiological side-effects such as eye strain, fatigue and nausea; resolves VAC.
- Bright in all environments: Holographic displays are very colourful at low power due to extremely high optical efficiency.
One of the most crucial features to consider when building an augmented reality (AR) display is realistic depth of field. In complex AR experiences where virtual images need to appear in the context of the real environment, using a realistic depth of field is required for the objects and scenes to match up and appear natural to the viewers. AR experiences must allow ‘world-locked content’ in which any virtual object can be placed at the exact depth it needs to be. In currently available AR wearables, virtual images are typically projected at a distance of 2 metres or optical infinity. While current AR wearables may adopt visual techniques such as stereoscopy to trick the eye into perceiving the object at accurate depth, the images will never precisely line up with the real world.
Vergence-accommodation conflict (VAC) is a prevalent issue that causes eye strain and headaches for many current AR wearables users. VAC is caused by the mismatch of cues between the depth at which the optical system tells a user to focus and the stereoscopic cue (the disparity between your eyes), which tells the user that the object is moving in and out of focus at different depths.
Holographic display delivers solutions to the issues in current AR wearables. Virtual images created using computer-generated holography are inherently three-dimensional and possess a natural depth of field, providing a solution to currently available AR headsets. Virtual objects and scenes presented on a holographic display can be placed at a distance between 10cm to the viewer, to optical infinity.
Related to depth of field is interactivity. Holographic display produces virtual objects that can be world-locked at any depth, creating intrinsically interactive AR experiences. To eliminate the need for intermediary interfaces to interact with objects in the future, displays should be intuitive, so that the user is able to reach out, grasp and place objects at any distance.
Another benefit of holographic display is its inherent high brightness. Computer-generated displays using phase LCoS devices are extremely power efficient for intrinsically high brightness. In holography, light is only directed into portions within the replay field where the holographic image is being projected. Holography is extremely power efficient, as light is not directed where it is not needed e.g. in backlit displays. In a paper released by VividQ in 2020, we confirm how it is possible to achieve >90% optical efficiency off the display and shows around 300,000 nits to the eye with microwatts of laser power. This is key to allow highly realistic images that are visible in all brightness settings, including outdoor environments.
How VividQ solved key challenges
In 2020, VividQ made considerable advancements in research and development to resolve three key issues related to traditional holographic display:
- Image quality: Holographic images produced using traditional methods of computer-generated holography often have low contrast, feature noise, speckle and artefacts due to the use of laser light, and ghost and conjugate images.
- Small field of view/eye box: The small etendue in the light creates difficult trade-offs between field of view and eye box size. Holographic display produces three-dimensional images, meaning it cannot benefit from using standard 2D eye box expansion.
- High compute power: In the past, holographic display required multiple high-end GPUs to run efficiently, drastically increasing its computational needs. This prevented it from targeting AR’s latency problems and preventing holography from running in real-time.
VividQ’s latest algorithms vastly improve image quality in holographic display, producing high contrast images with reduced speckle and noise, as well as colour balancing. Holographic images retain image resolution and full 3D information and can run in real-time. We have also solved a key issue in the trade-off between eye box and field of view. While the native eye box and field of view in holography was considered too small to be useful, our latest R&D work allows 3D images to be compatible with replicating waveguides for the first time.
Advancements in holographic display are being undertaken at Compound Photonics, a player in VividQ’s Partner Ecosystem. Edmund Passon, Co-CEO at Compound Photonics revealed during his own SPIE AR|VR|MR presentation how new developments in their microdisplay technology platforms now provide a means to extend a roadmap of current amplitude-modulating Liquid Crystal on Silicon (LCoS) all the way through to future holographic systems, while providing the required performance for real-time AR/MR systems.
To see Darran Milne’s SPIE AR|VR|MR 2021 presentation, click here. To read the summary of Darran’s SPIE Fireside chat, click here.
To learn more about applications of Computer-Generated Holography, download VividQ’s latest whitepaper, ‘Holography: The Future of Augmented Reality Wearables’ here.