How 3D LCD Shutter Technology Works

Liquid crystal shutter technology has been around for several years, but until recently was pretty much limited to CRT televisions due to high refresh rate requirements that could not be achieved with most LCD or plasma HDTVs. Today, both plasma and LCD televisions are available with high refresh rates, so the time is right for 3D home theater technology to play a much larger role in the consumer market.

There is a very good reason for covering LCD shutter technology today. At the recent 2009 Consumer Electronics Show (CES), several major manufacturers were showing 3D home theater entertainment solutions: Panasonic, Samsung and Sony. Two out of the three, Panasonic and Samsung, required the use of LCD shutter glasses to view the 3D effects.

In order to view any 3D movie using current technologies, you have to separate a left-eye view and a right-eye view into two distinct images that can only be viewed by the corresponding eye. Polarizing technologies are used in most movie theaters to separate the two images that are projected on the screen. LCD shutter technology uses special glasses that alternately apply a voltage to two liquid crystal lenses to darken the left lens while the right is transparent, and then darken the right lens while the left is transparent. This must happen at a very high rate in order to avoid a strobing effect. Currently, a minimum of a 120 Hz refresh rate is required so that action scenes appear to flow smoothly.

The process is referred to as alternate frame sequencing. A 120 Hz refresh rate splits the left-eye channel and the right-eye channel into two alternating views at 60 frames per second for each channel. Each lens on the LCD shutter glasses are synchronized to the appropriate image being displayed. Thus, the left eye only sees the left-eye image and right eye only sees the right-eye image. Although the refresh rate for the display is 120 times per second, the refresh rate for each lens of the shutter glasses is only 60 times per second.

There are two types of LCD glasses: wired and wireless. Due to the increased comfort and convenience of wireless glasses, that type was used with both the Panasonic and Samsung demonstrations at the 2009 Consumer Electronics Show. The LCD glasses used were slightly oversized and fit comfortably over my regular eyeglasses. They were very lightweight. Both Samsung and Panasonic shutter glasses used infrared technology and the glasses contained an IR sensor that picked up a signal from an emitter and synchronized the shuttering of the glasses to left/right framing of the images. At 120 Hz, there was no noticeable strobing or any indication that a framing process was taking place.

One benefit that I noticed about LCD shutter technology is that there really isn’t any of the ghosting that is noticeable when using an anaglyph image process for rendering 3D movies. Ghosting comes into play when you see part of the left image with the right eye and vice versa. In order for 3D movies to be enjoyable, distractions such as ghosting need to be minimized or eliminated.

On thing to note is that Samsung was showing a prototype model. The Samsung rep made it clear that this was not a product that was on its way to the market. The prototype was at CES to see how much interest there was in 3D viewing. From what I could see, there was a lot of interest. The Samsung rep also mentioned that the technology required the use of a Samsung 3D Ready HDTV. Those models include and Samsung 2007 or newer DLP models, or any 2008 Series 4 Samsung plasma display. I didn’t investigate this any further, but those are likely to be the models with at least a 120 Hz refresh rate.

Panasonic, however, was showing a product that they said is in development and will come to the market. I personally found the Panasonic model to be more enjoyable to watch, but part of that could have been the environment. Panasonic was showing their prototype in a movie theater, while Samsung’s 3D television was on the show floor. I think that further demonstrates which company is serious about pursuing 3D.