Liquid crystal shutter glasses have been around for a while and are emerging as the dominant technology for viewing 3D with the new 3D home theater technologies.
Liquid crystal shutter glasses–also called LC shutter glasses or active shutter glasses–use liquid crystal lenses that turn opaque when a voltage is applied. This process can occur very rapidly, which makes them ideal for the rapid transitions required for shutter glasses to work. Shutter glasses have several clear advantages over anaglyph 3D glasses technology, which uses two differently colored filters for lenses. Unlike anaglyph glasses that filter out some colors due to the colored lenses, liquid crystal glasses are color neutral, which means the full colors of the movie come through.
Shutter glasses work by alternately darkening one lens and then the other, varying each from transparent to opaque and then back to transparent. While one is opaque, the other is transparent, and vice versa. For the current 3D technology, these alternating transitions happen 120 times per second. Because this happens so fast, you cannot see the flickering of the lenses.
The reason why the lenses need to alternate from transparent to opaque is because in order to create the illusion of 3D stereoscopic movies, left-eye and a right-eye images need to be created on the HDTV or movie screen. The frame images displayed alternate at a rate of 120 times per second, which displays 60 left-eye perspective images alternately interlaced with 60 right-eye perspective images. This technique is called “alternate frame sequencing.” The shutter glasses are synchronized precisely to the left-eye and right-eye alternations on the screen, which creates the 3D illusion. Each eye only sees the version of the image (left or right perspective) that it needs to see at any given moment.
Modern shutter glasses are wireless and have a built-in receiver that receives a signal from an emitter that synchronizes the transitions. The technology is sometimes referred to as “active shutter” because of the electronic signal processing required for the process to work. Conversely, the use of either anaglyph 3D glasses or circularly polarized 3D glasses would be passive methods because no electronics or transitions are involved with the operation of the glasses.
LC shutter glasses technology is not knew. For several years a wide range of older movies have been available using a shutter glasses technology called HQFS (high quality field sequential) 3D or field sequential 3D. Many of the older 3D movies from the 1950s, as well as some fairly current movies, are available on standard DVD using this 3D approach. You can view a list of available HQFS movies at Amazon. The main difference with the field sequential 3D process is that the glasses are available with wired or wireless technology, and it is intended to work with standard televisions and DVDs with a refresh rate of 60 frames per second. HQFS glasses are not compatible with the current 3D technology.
One issue to note is that the new 3D active shutter glasses are not necessarily interchangeable and compatible with other manufacturer’s HDTVs. The re appears to be a compatibility problem with Panasonic shutter glasses and Samsung shutter glasses where they are out of phase with each other. If you are planning to purchase new 3D gear for your home theater, it might be wise to either purchase any additional glasses that you need from the manufacturer of your 3D HDTV, or find an alternative that works with your chosen HDTV brand. Each pair of shutter glasses currently costs about $150 when purchased from an HDTV manufacturer. Alternative brands are also beginning to show up that are priced closer to $100 per unit.