3D Displays Get Closer but Face Hurdles

HANK HOGAN, CONTRIBUTING EDITOR, hank.hogan@photonics.com

For viewers, a trip into the third dimension is getting cheaper and more satisfying. It also could be getting a lot nearer, driven by changes in photonics, optics and the market.

Further out lies the possibility of 3D displays that mimic what is seen when looking out a window. Research and development is underway to create such displays, which would require no glasses and perhaps no screens or imaging medium.

For now, though, commercially available 3D displays are stereoscopic, presenting different images to the left and right eyes to create a three-dimensional picture. This is done through glasses that passively filter or actively switch between the two different images.

Therein lies a problem.

“About 15 percent of people can’t see 3D using those current 3D technologies, which is a lot. One in seven is a lot. They get headaches, they get nauseous, or they just can’t see it,” said Edward Tang, chief strategy officer of Avegant Corp. of Belmont, Calif.

Privately held Avegant’s solution is to ditch the screen. Its wearable displays project images directly onto the retina. The result is similar to walking around with a portable 3D movie theater, according to Tang.

He said that the company’s recently launched flagship product, the Glyph, has its roots in a technology development project for the military. The Department of Defense wanted a display comfortable enough to be worn for hours while offering high resolution and low latency. The combination would enable crisp, low-eyestrain images even when viewing full-motion video.

Ninety percent fill factor

The researchers solved this with mirrors in a microelectromechanical system, or MEMS, device from Dallas-based Texas Instruments. The micromirror devices have a fill factor of 90 percent for all colors, far above the 15 to 20 percent per color typical for panel-based displays, Tang said. That and optics make it possible to hit an angular resolution of an arc minute, the limit of human vision. In effect, the pixels disappear.

The microscopic mirrors also reflect light from the ultraviolet to the infrared, giving the Avegant developers the freedom to use inexpensive and energy-efficient LEDs as a light source. Finally, the mirrors switch on and off in microseconds.

Several years ago the developers had a prototype, but they found that the content used for evaluation didn’t come from the military. “All the high-quality media that we were testing ended up being consumer media. Computer games, movies, graphics, things like that,” Tang said.

Consequently, the team opted to spin off Avegant to pursue commercial markets. The company’s developers shrank what was a copier-sized demonstrator down into something as big and about as heavy as a pair of high-end headphones.

A near-eye display in the form similar to high-end headphones enables personal viewing of 3D content. Courtesy of Avegant.

Some of the reasons why this could be done were ongoing improvements by Texas Instruments of the digital micromirror device in a digital light processing (DLP) chipset. Resolution has gone up, thanks in part to pixel sizes going down from 13 microns years ago to today’s 5.4. Also, with the right optics, this projection technology can be very compact in size, with the distance from the chip to the screen — or retina — being only a few millimeters, said Juan Alvarez, DLP product marketing engineer.

He noted that the chips can support the necessary frame rates for 3D, which are double that needed for 2D. The higher frame rate and resolution needed for 3D as compared to 2D impacts the entire display system.

“You have to pass more data through the whole system. But the good news is that technology has advanced not only at the display level, but also at the system technology level with faster data busses and processors,” Alvarez said.

Near-eye display vendors like Avegant, Vuzix of Rochester, N.Y., Oculus VR of Menlo Park, Calif., Magic Leap of Dania Beach, Fla., and others are developing 2D and 3D displays that could be used for augmented and virtual reality applications. They may benefit from a change in the market, with consumers increasingly accessing media via smartphones and other devices with small screens. The limitations of those screens make alternatives like headgear more attractive.

Such wearable 3D displays make possible new applications, such as looking through the camera on a drone to get a bird’s-eye view. By tracking where a user is looking, wearables could provide a view and enable control, creating the sensation of flying.

For all the attention that small screens garner, however, big displays represent much more real estate and a hefty market. According to IHS Markit, a technology and market research firm, large thin-film transistor LCD displays will decline in unit shipments from 2015 to 2016 but will still total more than 650 million units worldwide. Thus, there’s a large potential market for big screen 3D displays.

That potential is being held back by a lack of compelling content, cost and the fact that users currently have to wear glasses when watching 3D. A number of approaches are being investigated to get around these drawbacks.

For example, Provision Interactive Technologies of Chatsworth, Calif., uses proprietary technology to create floating imagery for digital signage applications, said CEO Curt Thornton. He added that the approach is derived from a 3D holographic display projection technique.

A hologram-based projection enables floating 3D imagery for digital signage. Courtesy of Provision Interactive Technologies.

Currently, the largest size of such displays is about 40 inches, with the image projected at a video frame rate about 36 inches away from the projector. The company is working to increase that size. A six-foot maximum would be about all that the current technology platform is capable of, Thornton said.

As for resolution, that runs about 1024 × 768 pixels. Thus, 2D displays today offer higher resolution, but what Provision Interactive Technologies provides is enough for the digital signage market, according to Thornton. He also noted that the company’s 3D technology is not limited to just that application.

“The broad brush of where we can go is anywhere where there is currently a traditional 2D flat panel, LCD or LED technology. We can go in and either replace, displace or supplement that technology,” Thornton said.

In another instance, a glasses-free three-dimensional display technology is being developed by 3DIcon Corp. of Tulsa, Okla. The company’s products send two infrared laser beams into an imaging medium, today composed of rare-earth-doped ZBLAN glass. At the point where the lasers intersect, two-photon absorption gives rise to fluorescence and the result is a 3D image.

Glasses-free 3D display technology could allow people to share and interact with a scene (above and at right). Courtesy of Holografika.

The challenge is that the imaging medium is not cheap. Hence, scaling demonstration systems up beyond a 4-cm cube is not economically practical. The company has therefore decided to develop proprietary silicone polymers, with the goal being the creation of one that has the right electrical and optical properties while meeting cost and weight targets.

“We believe we have a viable solution and that’s the direction we’re going right now,” said Doug Freitag, vice president of technology and business development.

As is presently done with the glass, the polymer will be doped with a rare earth to give it the right properties. The dopant will probably determine the final cost of the material. Freitag noted that the current approach looks promising, but a successful prototype must still be built. He added that the company is developing a family of polymers that could have a number of other uses, including depositing silicon films for flexible transistors in displays.

Two-photon absorption in an imaging medium gives rise to a 3D image, shown here in a medical display application. Courtesy of 3DIcon.

A final example of a glasses-free 3D display comes from Holografika Ltd. of Budapest, Hungary. CEO Tibor Balogh said that the company’s 3D light-field displays average 100 million pixels and can offer full-angle 180-degree viewing. The goal of Holografika’s founders was to create what Balogh characterized as the perfect 3D display.

Imagine hanging such a TV next to a window and that the scene being shown on the screen is what’s visible through the window. The ideal 3D display would have to pass a simple test. “You would not be able to differentiate if you are looking at the window or you are watching your TV set,” Balogh said.

He doesn’t claim perfection yet, but did indicate the company’s approach might make it possible. This would be done without the use of headgear, tracking or positioning and with the same comfort as watching any display today.

Courtesy of Holografika.

One problem is cost. A 3D display has many more pixels than a 2D one. In the case of Holografika’s approach, the ratio is about 100 to 1. So even if the company’s products are a 10th the cost on a per-pixel basis, the final price tag of its 3D displays will still be much higher than what it would be for a 2D one.

Holografika is making progress on this front, Balogh said. He added that the latest improvements in lowering costs make its displays suitable for high-end systems for professional applications. Further work could lower manufacturing expenses still more and that might lead to higher volume production and more cost-competitive displays.

He noted that while near-eye augmented and virtual reality generate publicity, such applications are inherently an isolated experience. A glasses-free approach, in contrast, enables whole groups to be immersed in what is being shown.

As Balogh said, “They can share the same 3D scene and they can interact with the scene in a natural way. With light-field you can do it.”