Technology Focus series: How can volumetric displays help utilise more information?

Volumetric displays are 3D visual representations that can be viewed from angle and without glasses or headsets. They are still in the development stages but have the potential to add value to current display technologies.

Latest update: January 2019

What are volumetric displays?

Volumetric displays are a branch of the 3D display family. A visual representation of an entity is created by the emission, scattering, or relaying of illumination throughout a 3D space (Holographic displays only scatter light at a 2D surface), with the emitters being co-located with the real image points. Volumetric displays can be viewed without glasses or headsets. The user can view the display from any angle because the emitters are co-located with the real image points. 

There are three main types of volumetric displays: Swept volume displays fuse rapidly oscillating or rotating 2D slices of an image to create a 3D display. Static volume displays use lasers/parallel light to generate a visible voxel (3D pixel) by rapidly scanning certain solids or gases to project an image. Recently, Free-space displays have been developed which do not require a specific substance to project into and can render a 3D image in normal air with no barrier between user and image.

What industries are using volumetric displays?

Small quantities of volumetric displays are being used in academia and various research labs, particularly the new free-space displays. Swept and static volume displays are slowly being commercialised. 

Voxon Photonics created a swept volume display in 2014. It can currently be purchased by the public for developing animated content, programming games and apps. Swept volume displays are targeting the medical industry to view and manipulate 3D scans including MRI and CT, benefiting from the spatial resolution and transparency as part of an interactive real time display.

Within the aviation industry, using 3D luggage visualisation at airport security could resolve any ambiguity by providing a clearer picture, hence reducing the need for further checks. It has also been suggested that air traffic control could use a static volume displays, such as a solid-state 3D computer monitor. The 3D display could map how planes are moving more accurately and intuitively compared to the 2D displays. Here, the sparse scene is well suited to the low bandwidth

In general, volumetric displays would fully utilise the 3D data which cannot be exploited in the current 2D displays. Volumetric displays could be applied to 3D geospatial analysis, benefiting many different types of operations such as oil and gas exploration, and preparation for natural disasters.

How will volumetric displays impact the rail industry?

Currently, volumetric displays are not ready for application in the rail industry however, future uses could include benefits to engineering projects. Solid-static volumetric computer displays could be used for Computer Aided Design or testing virtual prototypes. Swept volumetric displays or free-space displays such as the Optical trap display could provide a complete 3D image of the track or an engine. This could help with off-site training or preparation for rail infrastructure maintenance, hence reducing the length of time spent on the track or train, and the number of engineers required on site. Also, volumetric displays could be used in the cab to provide drivers with various real-time updates. 

Advances in intelligent display technology will personalise the customer’s experience. Volumetric displays, assisted by real time data, could provide virtual navigation to assist customers travelling around the network. A volumetric map or virtual concierge could be projected by devices in the station or the customer’s phone to direct them to their required destination. Since volumetric displays can be turned off, they avoid causing an obstruction.

What should the rail industry do?

Volumetric display technology is quite far off from being ready, but it has the potential to add value to current display technologies. When it is developed and economically viable, integration will most likely be undertaken by display companies. Hence, the industry does not need to adjust investment decisions based on this technology developing. Nevertheless, the industry should monitor technological and patent developments to help determine what further developments in this technology would mean for rail, for example, monitoring the rail network or infrastructure maintenance

What is the current state of R&D?

Researchers at Brigham Young University, USA, developed the Optical trap display (2018), a free-space volumetric display. These are based on photophoretic optical trapping that produces full-colour graphics in free space. The next stage of development is to trap and illuminate multiple particles at once to increase the size and image sophistication. 

The Coretec Group have created a monochrome laboratory prototype of a glass free static volumetric display, which is visible in ambient lighting with a 4cm3 image size.

What uncertainties of volumetric displays remain?

Volumetric displays are still in the development stages. Further research into the manufacturing process of volumetric displays will be required to improve the scale, quality and cost. Applications of volumetric displays are currently limited by their size and scale. For example, the display size of Voxon Photonics’ swept display is only 18x18x8 cm and the prototype Optical-trap display is even smaller at 1cm3

Volumetric displays require more bandwidth than 2D imagery of equivalent quality. To create colour images on the multiple image planes, the single-chip engine must run faster. Currently, the interface bandwidth limits the data distributed to the display and colour images are produced with low colour depths.

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