Hologram telephone booths: Well-known theatre tricks are given a new digital life

Illustration: PORTL

After a year and a half of video meetings, webinars, and online conferences, it can be difficult to stay focused on a flat 2D screen at work or at home on the couch. This gave rise to new display solutions that approach 3D formats, but without virtual reality headsets.

Ingeniøren has taken a closer look at the solutions that are emerging right now. We start in Los Angeles, where PORTL has launched a telephone-booth-like case that can display a digital speaker in a scale of 1:1. The case is just over two meters high, 60 centimetres deep, and fully lined with transparent liquid-crystal displays—LCDs.

“The key to the 3D effect are transparent LCD lights from which the crystal substrate is removed. The illusion is created due to the powerful rear case, which contains a deep empty space that is brightly lit from all sides. At the same time, an acrylic plate is placed in front of the person being recorded, so that the lower part of their body is reflected on a 2D screen. It works surprisingly well, and the brain thinks that it sees depth, even though this is not really the case,” explains Peter Simonsen, co-founder and head of R&D at the Danish company Realfiction, which develops holographic 3D solutions.

This type of transparent LCD cases has been on the market for a number of years, but often in smaller formats.

“The price of LCD screens has plummeted in recent years, so this type of specially designed displays can now be made without the process becoming exorbitantly expensive. We all stare at screens for many hours a day, which is why the 3D feeling has an effect on the brain, and this sharpens our senses and improves our concentration, so we can better communicate and tell stories,” Peter Simonsen says.

The telephone-booth-like case is called PORTL Epic, and it consists of a cabinet that weighs about 180 kilograms, is 2.1 meters high, 1.5 meters wide and 60 centimetres deep. The back wall of the case is white, just like the person projected as a hologram is recorded on a white background.

The solution costs close to DKK 400 000 and has the disadvantage of not having the feeling of standing or sitting next to the person who is encapsulated by the box.

Transparent backdrop

Another similar solution is the HoloPod by the Canadian company ARHT, which uses a slightly different type of optical illusion, namely a transparent backdrop.

“They use an old theatre technique with perforated semi-transparent backdrops. One can make patterns and draw on the backdrop with projected light, so that vivid silhouettes appear on the stage. It may seem a bit old-fashioned to project light onto a piece of cloth, but if you want to achieve the same effect with electronics, it starts to get difficult,” Peter Simonsen says.

Back in the early 00s, he himself co-founded a company that developed a similar solution with perforated backdrops.

But so far, transparent materials are still more functional than electronic solutions with OLED display technology, which is also transparent.

Here, the challenge is that the sharpness of the background seen through the display disappears when you move more than two meters away from it, and the OLED display size rarely exceeds 100 inches.

But are these old theatre techniques being revived in new digital formats just now?

“It’s time to try to update the old traditional TV formats with extra layers. PORTL and ARHT are two good takes on how to create 3D effects with the available display technology,” says Steen Iversen, director of Advanced Display Technology at Realfiction.

Danish holography

Realfiction has slightly more ambitious plans than PORTL and ARHT. They want to design and develop a true holographic TV screen with directional pixels using already existing thin film technology.

“We have developed an OLED pixel that can send light out in precise directions. We are not the first to do that, but our solution has a higher resolution and can be implemented in well-known flat screens,” Steen Iversen says.

The project is called Echo and has recently received DKK five million in support from Innovation Fund Denmark.

Realfiction uses eye tracking to provide a true holographic experience where one can move around an object, so they always know which eye is viewing the screen and from which position.

Illustration: Realfiction

The underlying pixel technology is called “light field display”, where different light is emitted in different directions so that one eye sees a pixel in one colour, while the other eye sees a different colour. If you move around, you see other colours again.

However, no one has yet been successful in achieving a real breakthrough with light field displays, partly due to the high cost and the relatively low resolution, both in terms of the image itself and angular resolution. In the best light field display prototypes, light is emitted in, for example, 50x50, i.e. 2500 directions simultaneously. This provides a very limited image resolution of a few hundred pixels in width. The problem is the bandwidth of the display. It already takes many millions of thin film transistors to connect the circuits in an OLED screen and squeezing in 2500 times as many transistors is completely unrealistic today. The eye tracking technology at Realfiction solves a part of that challenge because it is not necessary to emit light in all directions, but only in the areas where eyes are directed to.

Realfiction has today demonstrated proof of concepts in a scale of 20:1 with 400 monochrome pixels.

“It was a great success, even though probably only electrical engineers would appreciate the setup. Since then, we have also made a small demo with a turtle that swam in an aquarium that you could move around,” Steen Iversen says.
Realfiction decided to invest in OLED display technology, as the speed is significantly higher than in LCDs.

“We need a display with up to around 600 frames per second. Even the most demanding gamers don’t need more than 240 hertz. But if several people want to use the same screen at the same time, then high speed and very low latency are needed. When the screen runs at 600 frames per second, that is enough to deliver 60 frames per second for ten eyes, i.e. five people. Our system is not only dependent on pixels and thin film technology, but also on high demands for the entire transmission chain, so we can maintain the holographic effect,” Steen Iversen says.

Over the past year, Realfiction has spent time on the organizational setup—they founded a development consortium with the Belgian company Imec based in Leuven and the German company Fraunhofer FEP based in Dresden, and they also hired two thin film specialists who are working from Taiwan.

“In ten years, I think many will have replaced their computers with augmented reality glasses, which have imported the operating systems we know from computers and smartphones. The Internet is becoming volumetric. With our solution, you can share holographic content without glasses, and thus more people can view the same content on the same screen,” Peter Simonsen says.