LG Shows Full Range of 3D LCDs

LG Electronics put on an impressive show of 3D-LCD displays at the 2009 Society for Information Display (SID) conference this year, showcasing four different types of glasses-based 3D and one AS-3D display. This demo shows that several approaches are maturing simultaneously to help enable many 3D consumer market applications.

23-inch Active Shutter Glasses
This monitor is a 1920- x 1080-resolution 23-inch panel that operates with active shutter glasses. It is perhaps the closest to commercialization, as it is in the process of being certified by NVIDIA. We were told this is about one to two months from a formal introduction.

As shown in the block diagram, data for the left-eye image is sent to the panel so all rows can be updated. This data is then held in place for a certain time (VBT or Vertical Blanking Time), so that the shutter can be opened for that eye image. As can be seen, the light “on” time for the shutter glasses is a small percentage of time (the area under the square pulse). This means a lower light level for the eye vs. 2D mode unless the backlight can be driven much harder during this brief “on” period.

Specs for the display were listed as 96-ppi pixel density, 16M colors (6-bit + A-FRC), 72 percent color gamut, 400 cd/m2 brightness (3D-mode brightness not specified but it is probably 60 - 80 cd/m2), 3.5 ms gray-to-gray, 1,000:1 contrast and 170/160 degree viewing angles using LG’s IPM mode. This display looks quite good.

24-inch Patterned Retarder 3D Display
LG calls its version of the micro-pol or X-pol type of 3D display a “Patterned Retarder” type. Its operation is shown in the diagram. The micro-pol array produces left images from even rows and right images from odd rows, each with orthogonal circular polarization. The user wears passive polarized glasses to separate the images. The 3D signal is supplied to the display in a line-interleaved format.



On display at SID was a 24-inch monitor with a resolution of 1920 x 1200 in 2D, which becomes 1920 x 600 per eye in 3D. Brightness is specified as 350 cd/m2 without the glasses and 130 cd/m2 with the glasses. The color gamut is 102%, suggesting an LED backlight and an anti-reflection coating is applied.

This approach can compete with the active-shutter glasses approach above for gaming and other PC monitor applications. The advantage of this approach is the lower cost of the passive glasses, higher brightness and wider color gamut. The disadvantage is likely to be cost and lower resolution per eye. Micro-pol monitors may also introduce some distortion when viewing 2D content.

47-inch Human Friendly 3D Display
The next demo was what LG called its “Human Friendly” 3D display. This is a 47-inch FHD panel that is fitted with a micro-pol array and an IR receiver. The user wears passive polarized glasses outfitted with IR transmitters on each side of the glasses. The sensor receives the signals from the glasses and uses the data to track the user’s position. The positional data adjusts the 3D view based on the users position with respect to the display.

As illustrated in the figure, viewers on the left side of the display see one side of the plane, while viewers on the right side see the other side of the plane. LG did not say how many views it could show, but it was clearly not a real-time update of the content. The tracking seemed fast enough, but the movement from view to view was in discrete steps and not smooth at all.



Specifications for the demo included 1920 x 1080 resolution for 2D, 1920 x 540 for 3D, brightness of 450 cd/m2 for 2D and 200 cd/m2 for 3D, one billion colors via 10 bit processing and an anti-reflection coating. The tracking system can work over an 80-degree horizontal angle with the user being less than four meters away. The best viewing distance is also one to four meters from the display. The demo used a DDD game driver with the Microsoft Flight Simulator application.

23-inch 3D Active Retarder
One of the more innovative displays in the LG booth was one labeled “Active Retarder.” We revealed this display in the June issue of Large Display Report and saw it at SID. There was also a paper given in the technical symposium that covered this device.

On the show floor, the display showed well, but there was some visible ghosting. It allows for FHD (1920 x 1080) resolution in both 2D and 3D mode, but the brightness drops from 390 cd/m2 in 2D to 90 cd/m2 in 3D mode. This is a result of the way the panel and active shutter glasses are constructed and driven.

Basically, the idea is to place an active switch over the LCD panel to rotate the polarization state of the output in a time-sequential manner. This allows passive-polarized glasses to be used.

If a single cell switch with TN, pi-cell or ECB modes were used to do this, there would usually be a mixture of left- and right-eye data on the screen, creating very high crosstalk. To avoid this, it is better to create a series of narrow, wide active retarders that are sequenced “on” as the rows underneath them are updated. Bands are activated or turned off from top to bottom, following the row update timing.

This is done first for the right-eye data with the retarders activated to pass the input polarized light in the same state. For the left-eye data in the next frame, the retarder is activated to output at an orthogonal polarization state so the other eye can see the image. As before, the active retarders are turned on in sequence as the rows underneath them are updated. Data should be presented at 120Hz in a page-flipping, time-sequential format; however, it is believed that data was presented at 180Hz.



The main advantage of this approach is the ability to use passive-polarized glasses and to create a 3D display with much higher brightness than those with active-shutter glasses.

In the paper given in the symposium, LG described a 15-inch prototype made using retarders with a TN mode, but said it is now looking at other LC modes.

Cross talk for the 15-inch (and perhaps for the 23-inch) was a rather high 3.5%, which represented an average of the left and right crosstalk measurements. Apparently, the right eye has more crosstalk than the left eye (15.8 vs. 0.8% for the 15-inch).

47-inch Switchable Lens AS-3D
A 47-inch switchable lens type 3D-LCD also was shown at SID. This device features a basic FHD panel with a second layer that allows for the creation of a lenticular lens by voltage control. The advantage of this approach is that there should be little light loss (LG says it is the same in 2D or 3D mode at 550 cd/m2) and it may perform better as a 2D display. This display was clearly a lot brighter than any of the other 3D displays.

LG did not reveal any details on how it constructed the switchable lens, but other groups presented papers on their approaches. The demo featured a nine-view implementation with the optimized viewing distance of two to three meters. Resolution (theoretical) per view was stated as 426 x 540. Transitions from view zone to view zone were noticeable and a bit jumpy.

Summary
LG presented three of the four leading solutions for LCDs for 3D monitors and TVs using glasses. The patterned-retarder micropol approach was the brightest (130 cd/m2), with the 120-Hz active-shutter glasses and the active retarder having 90 cd/m2 or less brightness. The shutter glass approach is closest to market with the active retarder still needing development. The patterned retarder may be the most expensive and offers one-half resolution per eye.

What LG did not show was a two-panel (front/back) type solution such as has been commercialized by iZ3D. All in all, an impressive 3D showing by LG.

By Chris Chinnock, Insight Media