Developers forge ahead with both stereoscopic and autostereoscopic applications, with an emphasis on eye tracking.

by Steve Sechrist

3-D was a recurring theme at SID's Display Week in Boston this year, from the opening keynote address to the Best-in-Show awards, to the exhibition floor, and in the technical and business conference sessions as well. Examples of both glasses-based and autostereoscopic 3-D were presented. And if Display Week 2012 is a reliable signpost, the road to high-performance glasses-free 3-D displays will be paved by efficient eye-tracking technology.

The Eyes Track It

At Display Week's Business Conference, hosted by IMS Research, AU Optronics introduced its next-generation eye-tracking autostereoscopic technology in a presentation from Wei-Leung Liau, Associate Vice-President at AUO's Display Technology Development Center. Liau described the evolution of 3-D displays and provided an overview of conventional glasses-free 3-D technology as well as highlights from AUO's high-resolution eye-tracking technology. Stating that consumers ultimately want the burden of glasses removed from the 3-D viewing process, he characterized the major drawback of conventional lens and barrier approaches to autostereo: dead zones, ghosting images, and resolution loss as viewing zones increase.

AUO's solution has been to develop an eye-tracking technology in conjunction with a switchable lenticular lens. To get there, the company created an image algorithm chip and eye-tracking camera that shift the 3-D sweet spot to where the viewer is looking (Fig. 1). AUO showed this technology at Display Taiwan last June in a laptop prototype and I saw it again at CES 2012 in January in a Sony device. The Sony product manager confirmed the AUO source at that time, as the interface software used was unmistakable. According to AUO, the benefits of using an eye-tracking solution for autostereo include a dead-zone-free environment, high-resolution 2-D (full HD)/3-D (HD), normal frame rate, high brightness, and 2-D/3-D switchability.

Fig. 1: AUO's popular eye-tracking technology uses an image algorithm chip in combination with a camera.

The company is also planning to create a "local 3-D window" within a display. This would allow a portion of a display screen to show 3-D while the rest of the image remains in 2-D. It's a feature that was demonstrated by others at Display Week (shown at the NLT/Renesas booth in the exhibition, for example) and is aimed at advertisers who can use the application to show off product features and to call attention to specific ads.

Elsewhere on the floor, LG was showing off a 4.5-in. autostereoscopic-display prototype that used eye tracking to deliver what the company billed as a "Viewing Angle Free 3-D" image. The prototype panel came mounted inside a package housing a camera used to generate the face/eye-tracking data. LG Researcher Dongkyu Kim said the device initially was created to convince the LG team of the viability of this approach, which will eventually be built into a next-generation 7–10-in. tablet display. Limited specs were available on the prototype, but I did learn that the horizontal and vertical viewing angles were 48° and the optimal viewing distance for this size panel was at 30–35 cm.

One of the most noticeable indicators of the importance of both 3-D and eye tracking at Display Week this year came when Dimenco received a Best-in-Show award for its "Dynamic View" technology. The company's 23-in. autostereoscopic gaming monitor switches between a single (eye tracking) or multi-user autostereo 3-D image for viewing high-resolution games, film, or TV content. (For more about this product, see the Best-in-Show article in this issue.)

There were also some notable papers from the technical sessions that featured 3-D with eye tracking or face tracking. "Hardware and Software Technologies for Glasses-Free 3-D TVs and PCs" by G. Ito from Toshiba's R&D Center outlined both hardware and software solutions for the company's portrait/landscape switchable display now in mass production. Topics included a one-dimensional integral imaging method, a new moiré-free pixel design using a vertical lenticular sheet, 2-D/3-D switching with a liquid-crystal gradient index (LC GRIN) lens (showing uses in its 3-D panels), 2-D/3-D image conversion, face tracking for 3-D viewing zone shift, and 3-D super-resolution image processing.

C. H. Yang from the Department of Photonics at National Chiao Tung University presented the late-news paper "High Resolution Time-multiplexed Backlight with Tracking System for Multi-user Applicable Wide-viewing Autostereoscopic LCD." Notable was the work done to address the commonly observed problems of limited 3-D viewing angle and fixed-position observer locations. The proposed solution was a combination of an adjustable fine-stripe (AFS) backlight, a lenticular lens, and a 120-Hz LCD with sufficient resolution to deliver a wide viewing angle for multi-user autostereoscopic applications. The trick is to use a camera for eye tracking of multiple viewers. According to author Yang, "…each strip on the AFS backlight can turn on and off individually. The function of the lenticular lens is to direct the light of different strips into the different viewpoints," as the AFS backlight is adjusted to project light to different users. Yang said since the tracking system can locate the viewer's position, the time-multiplexed display can project a temporal two-view image to each user while maintaining high resolution and increasing viewing angles for multi-users simultaneously.

Technically 3-D

The above were just two of the exciting papers presented at Display Week. In all, the technical Symposium featured no fewer than 12 3-D sessions with four papers each. These included distinguished and invited papers highlighted at the show by respective committee chairpersons for special recognition.

LG Display and Sharp pointed to the future direction of 3-D TVs in two Distinguished Papers focusing on autostereo. In "Development of Super Hi-Vision 8K x 4K Direct-View LCD for Next-Generation TV," Sharp Corporation's T. Kamakura and team described their 8K x 4K (7680 x 4320) resolution Super Hi-Vision UHD LCD offering 16x the resolution of a Full-HD system in a whopping 85-in.-diagonal display. The company said the panel has 103 ppi and a luminance of 300 cd/m². Other features include an aspect ratio of 16:9, 10-bit RGB color, and 60-Hz operations. The display also uses an RGB LED backlight.

LG Display presented "Implementation of 240-Hz 55-in. Ultra-Definition LCD Driven by a-IGZO Semiconductor TFT with Copper Signal Lines." Author N. Gong said in his talk, "As the resolution and the frame rate of a panel increase, pixel charging time and panel transmittance ratio decrease." The paper shows how LG implemented a 55-in. LCD TV with 240 Hz and an impressive 3840 x 2160 resolution, using a metal-oxide (IGZO) backplane (IGZO TFT and copper metallization.) According to Gong, the group investigated three panel-driving architectures, concluding that a bus-line architecture with 1G1D (one gate one driver) works best, delivering a line time for a 240-Hz refresh rate of just 1.6 μsec from a double-bank IC connection. This approach offers the promise to deliver "… cost benefit, process competitiveness, and design flexibility," Gong said. It can also be mass-produced on existing a-Si TFT lines "… with minor modifications." This is partly due to prior development done by LG in the copper metallization process for an a-IGZO TFT. His talk also covered solutions to the problem of charge time for each pixel, reduced by half "…just by doubling the number of gate scan lines" and offered an explanation of the company's panel fabrication of the oxide TFT manufacturing process using an inverted-staggered bottom-gate structure. Their efforts paid off in developing a UD AMLCD panel in a 55-in. prototype that Gong concluded, "proved that a-IGZO TFT, IPS mode, and copper metallization technology is very promising for the large-sized high-resolution TVs."

"Displays Using Scanning Laser Projection" by Dr. Brian Schowengerdt et al. from the Department of Mechanical Engineering at the University of Washington covered advances in 3-D using several devices built from multiple scanned laser projectors. One consists of "…arrays of scanning fiber projectors [that] can enable massively multi-view autostereoscopic displays with full head- motion parallax and partial accommodation cues," Schowengerdt said. The group also developed a head-mounted display in the lab that incorporates a 1 mm x 9 mm projector that can fit within the temples of eyeglasses and "…uses a vibrating single-mode optical fiber to produce scanned images," that Schowengerdt calls "the smallest display in the world."

3-D Visions Large and Small

The 3-D developments presented at Display Week started off with a far-ranging talk and included displays of all sizes on the show floor. The event began with a visionary keynote address by Ramash Raskar of MIT Media Lab's Center for Future Storytelling, who discussed novel display developments based on work done at the Lab's Camera Culture Group as well as at Mitsubishi's (MERL) R&D lab. One of the most exciting is a "shift glass" approach that touches the very frontiers of optics. This approach involves shifting the physics (space, wavelength, time, and light) of a display; the results could eventually be applied to autostereoscopic panels. The MIT group has also developed and studied light-sensitive displays, multi-touch/gesture-driven interactive displays, and autostereoscopic 3-D displays using lenslet arrays and layered light-bending masks.

In the exhibit hall, there were lots of 3-D options for next-generation mobile devices and other small display applications. In the NLT/Renesas Electronics booth was an autostereoscopic LCD in a 3.1-in. WQVGA (400 x 240) prototype that offered six views – a lot from a relatively small (high-resolution) display. Renesas Display engineer Dale Maunu said the LCD uses an LTPS backplane and features a new "HxDP" pixel array (horizontally x times – density pixels). The panel uses a lenticular lens to accommodate the unique horizontal RGB stripe that generates the 3-D image. The module uses RGB color pixels, with three subpixels each, which are striped horizontally and split in sixths lengthwise. This delivers a resolution 6x times that of conventional (vertically striped) 3-D LCD panels. NLT's HxDP technology is an outgrowth of the HDDP (horizontally double-density pixels) technology originally used in the company's multi-view displays (Fig. 2).

Fig. 2: HxDP is shown in three operation modes. Source: NLT.

Chimei Innolux (CMI) was showing a 4.3-in. LCD panel with switchable barrier technology delivering an autostereoscopic image that channels light through a cell-gap pixel structure. In the on-state it generates a left-eye/right-eye image for on-axis viewing, but delivers simultaneously a decent 2-D image for any off-axis viewing. In the off-mode, a standard (higher resolution) 2D view is created that solves the problem of one-viewer-only images, particularly on larger mobile displays such as tablets. The group claims its novel approach delivers a wide 3-D viewing angle, low 3-D crosstalk, and low 3-D moiré. There are other multi-mode 3-D systems that seek to serve specific user needs (Dimenco for one), but CMI is delivering its product without the use of eye tracking, which could possibly prove to have advantages in cost, processing, and power savings – all key issues in mobile applications (Fig. 3).

Fig. 3: CMI's barrier approach switches between 2-D and 3-D. Source: Author/CMI.

Another attention getter in the Dimenco booth (besides the Best-in-Show winner) was a 56-in. 4K x 2K 3-D TV offering 28-view autostereo with adopted Dolby 3-D technology. Dimenco said the Dolby implementation was part of a combined project between Dolby Labs and Royal Philips Electronics, using the Dolby 3-D HD technology suite. The company also showed a 55-in. tiled 3-D video wall, using a narrow-bezel display that is designed to target digital signage and other large installation applications.

There were two other displays on the show floor that were offering 3-D options with glasses that could hardly be missed: Samsung's 55-in. AMOLED TV with RGB OLEDs and LTPS backplane and Smart Dual-View feature and LG Display's 55-in. AMOLED TV with white OLEDs and the oxide backplane in a thin form factor. Both won Best-in-Show awards.

Samsung's 55-in. AMOLED TV has been written about in the OLED Technology Review in this issue, but I wanted to note that the AMOLED display was one of the brightest on the show floor and emitted a highly saturated (almost too saturated) color image. While in 3-D, the image looked spectacular, perhaps because it may have toned down the (oversaturated) colors when the display was shown in 2-D.

A particularly interesting aspect of the new display was how Samsung took the concept of 3-D delivery to new heights with its Smart Dual-View feature that uses the active 3-D technology on its new OLED TVs for simultaneous dual viewing. By applying the left-eye/right-eye glasses approach, the company created a technology that allows two completely different Full HD programs to be viewed on the same set, at the same time.

Samsung also debuted new active 3-D glasses designs that remove weight and bulk from the wearer's face, moving most of its discrete electronics to the "arms" of the glasses that rest on the ears. The result is a well-balanced feather-like feel, which goes a long way toward making active glasses more acceptable.

LG was also on hand with a 55-in. AMOLED TV based on WRGB OLEDs with an IGZO (metal-oxide active-matrix) backplane. The company claims this combination of using white OLEDs and color filter together with the metal-oxide backplane should give it a manufacturing price advantage over alternative approaches (this is a reference to the Samsung LTPS backplane methodology). LG uses a passive 3-D technology with a film-patterned retarder and low-cost glasses. The company is planning mass production this year, and as mentioned earlier, took home a Best-in-Show award, as did Samsung. For more on these two units, also see this issue's Best-in-Show article.

The Future of 3-D

Most experts agree that the bottom line to delivering autostereo in the near term will depend on higher-resolution and faster-addressing displays and perhaps will include some form of eye-tracking technology. As evidenced at Display Week, we can look forward to continued progress in these areas, as developers push the display technology envelope, edging us ever closer to autostereoscopic display nirvana. Suffice it to say the best and brightest in the category were on their game at Display Week in Boston, and it's a solid bet that a future glimpse of mainstream 3-D display technology could already be touched and more importantly viewed at the groundbreaking event. •